Herd immunity without vaccines? (corona question)

Herd immunity without vaccines? (corona question)

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Obviously there is herd immunity against many viruses such as measles because of vaccines.

Can we say that there is herd immunity against any particular virus even though people are not getting vaccinated, and what virus would that be?

Do you typically get herd immunity without vaccines against viruses without vaccines or do the viruses just linger around and infect fewer people because many have already become immune after catching the virus and developing anti-bodies?

What is "normal" virus behaviour?

This is not just a corona related question, this is true for each disease which is can be transmitted easily and which builds up a lasting immunity.

Herd immunity per se means that a large proportion of a given population is immune to a given disease, either because of vaccination or because the population went through the disease, survived it and built up lasting immunity. This means that even when this disease comes around again, it will only infect few people who have no immunity, but will not spread through the population. This can be seen in the figure below (from here), which implies vaccination, but works as well with getting the disease.

The first case is what happens right now with SARS-CoV-2, it is a new disease to which no one has immunity, so everybody who gets in contact will get the disease (either more or less severe).

If no vaccine would be available, this infection would go on, until a big enough proportion of the population has gone through the infection, developed immunity and thus stops the spread (go to the third part of the figure). At this point a big pandemie would stop.

However, this strategy has one problem: People who are coming into the population (newborns for example) who have no immunity are susceptible for the disease. This ensures low level infection rates and will make sure that the disease will stay in the population, but mostly not noticable. Over time the number of not immune people will rise until there are enough of them to feed another big breakout.

As @bryankrause pointed out, in the past getting to the point to reach herd immunity (at least partly) for diseases like smallpox or measles and to maintain it, cost a lot of lifes.

This is exactly what can be seen in the number of measles cases before the introduction of the vaccine in 1967. Before vaccination every 18 - 24 months enough people without immunity where present, causing another wave of cases. After introducing the vaccination this pattern changes and case numbers went down drastically. See the figure (from reference 1) for illustration. This figure uses data from the US, but you see similar pattern in the rest of the world.

For some more information have a look at reference 2.


  1. Evolution of measles elimination strategies in the United States.
  2. Vaccination and herd immunity: what more do we know?

By Gypsyamber D’Souza and David Dowdy | Updated April 6, 2021

When the coronavirus that causes COVID-19 first started to spread, virtually nobody was immune. Meeting no resistance, the virus spread quickly across communities. Stopping it will require a significant percentage of people to be immune. But how can we get to that point?

In this Q&A, Gypsyamber D’Souza, PhD ’07, MPH, MS, and David Dowdy, MD, PhD ’08, ScM ’02, explain how the race is on to get people immune by vaccinating them before they get infected.

What is herd immunity?

When most of a population is immune to an infectious disease, this provides indirect protection—or population immunity (also called herd immunity or herd protection)—to those who are not immune to the disease.

For example, if 80% of a population is immune to a virus, four out of every five people who encounter someone with the disease won’t get sick (and won’t spread the disease any further). In this way, the spread of infectious diseases is kept under control. Depending how contagious an infection is, usually 50% to 90% of a population needs immunity before infection rates start to decline. But this percentage isn’t a “magic threshold” that we need to cross—especially for a novel virus. Both viral evolution and changes in how people interact with each other can bring this number up or down. Below any “herd immunity threshold,” immunity in the population (for example, from vaccination) can still have a positive effect. And above the threshold, infections can still occur.

The higher the level of immunity, the larger the benefit. This is why it is important to get as many people as possible vaccinated.

How have we achieved herd immunity for other infectious diseases?

Measles, mumps, polio, and chickenpox are examples of infectious diseases that were once very common but are now rare in the U.S. because vaccines helped to establish herd immunity. We sometimes see outbreaks of vaccine-preventable diseases in communities with lower vaccine coverage because they don’t have herd protection. (The 2019 measles outbreak at Disneyland is an example.)

For infections without a vaccine, even if many adults have developed immunity because of prior infection, the disease can still circulate among children and can still infect those with weakened immune systems. This was seen for many of the aforementioned diseases before vaccines were developed.

Other viruses (like the flu) mutate over time, so antibodies from a previous infection provide protection for only a short period of time. For the flu, this is less than a year. If SARS-CoV-2, the virus that causes COVID-19, is like other coronaviruses that currently infect humans, we can expect that people who get infected will be immune for months to years. For example, population-based studies in places like Denmark have shown that an initial infection by SARS-CoV-2 is protective against repeat infection for more than six months. But this level of immunity may be lower among people with weaker immune systems (such as people who are older), and it is unlikely to be lifelong. This is why we need vaccines for SARS-CoV-2 as well.

What will it take to achieve herd immunity with SARS-CoV-2?

As with any other infection, there are two ways to achieve herd immunity: A large proportion of the population either gets infected or gets a protective vaccine. What we know about coronavirus so far suggests that, if we were really to go back to a pre-pandemic lifestyle, we would need at least 70% of the population to be immune to keep the rate of infection down (“achieve herd immunity”) without restrictions on activities. But this level depends on many factors, including the infectiousness of the virus (variants can evolve that are more infectious) and how people interact with each other.

For example, when the population reduces their level of interaction (through distancing, wearing masks, etc.), infection rates slow down. But as society opens up more broadly and the virus mutates to become more contagious, infection rates will go up again. Since we are not currently at a level of protection that can allow life to return to normal without seeing another spike in cases and deaths, it is now a race between infection and injection.

What are the possibilities for how herd immunity could play out?

In the worst case (for example, if we stop distancing and mask wearing and remove limits on crowded indoor gatherings), we will continue to see additional waves of surging infection. The virus will infect—and kill—many more people before our vaccination program reaches everyone. And deaths aren’t the only problem. The more people the virus infects, the more chances it has to mutate. This can increase transmission risk, decrease the effectiveness of vaccines, and make the pandemic harder to control in the long run.

In the best case, we vaccinate people as quickly as possible while maintaining distancing and other prevention measures to keep infection levels low. This will take concerted effort on everyone’s part. But if we continue vaccinating the population at the current rate, in the U.S. we should see meaningful effects on transmission by the end of the summer of 2021. While there is not going to be a “herd immunity day” where life immediately goes back to normal, this approach gives us the best long-term chance of beating the pandemic.

The most likely outcome is somewhere in the middle of these extremes. During the spring and early summer (or longer, if efforts to vaccinate the population stall), we will likely continue to see infection rates rise and fall. When infection rates fall, we may relax distancing measures—but this can lead to a rebound in infections as people interact with each other more closely. We then may need to re-implement these measures to bring infections down again.

Will we ever get to herd immunity?

Yes—and hopefully sooner rather than later, as vaccine manufacturing and distribution are rapidly being scaled up. In the United States, current projections are that we can get more than half of all American adults fully vaccinated by the end of Summer 2021—which would take us a long way toward herd immunity, in only a few months. By the time winter comes around, hopefully enough of the population will be vaccinated to prevent another large surge like what we have seen this year. But this optimistic scenario is not guaranteed. It requires widespread vaccine uptake among all parts of the population—including all ages and races, in all cities, suburbs, and countrysides. Because the human population is so interconnected, an outbreak anywhere can lead to a resurgence everywhere.

This is a global concern as well. As long as there are unvaccinated populations in the world, SARS-CoV-2 will continue to spread and mutate, and additional variants will emerge. In the U.S. and elsewhere, booster vaccination may become necessary if variants arise that can evade the immune response provoked by current vaccines.

Prolonged effort will be required to prevent major outbreaks until vaccination is widespread. Even then, it is very unlikely that SARS-CoV-2 will be eradicated it will still likely infect children and others who have not been vaccinated, and we will likely need to update the vaccine and provide booster doses on some regular basis. But it is also likely that the continuing waves of explosive spread that we are seeing right now will eventually die down—because in the future, enough of the population will be immune to provide herd protection.

What should we expect in the coming months?

We now have multiple effective vaccines, and the race is on to get people vaccinated before they get infected (and have the chance to spread infection to others). It is difficult to predict the future because many factors are at play—including new variants with the potential for increased transmission, changes in our own behavior as the pandemic drags on, and seasonal effects that may help to reduce transmission in the summer months. But one thing is certain: The more people who are vaccinated, the less opportunity the virus will have to spread in the population, and the closer we will be to herd immunity.

We have seen that the restrictions needed over time have varied as preventive measures have worked to drive infection rates down, but we have also seen these rates resurge as our responses have relaxed. Once we get enough people vaccinated to drive down infection rates more consistently, we should be able to gradually lift these restrictions. But until the vaccine is widely distributed and a large majority of the population is vaccinated, there will still be a risk of infection and outbreaks—and we will need to take some precautions.

In the end, though, we will build up immunity to this virus life will be able to return to “normal” eventually. The fastest way to get to that point is for each of us to do our part in the coming months to reduce the spread of the virus—continue to wear masks, maintain distance, avoid high-risk indoor gatherings, and get vaccinated as soon as a vaccine becomes available to us.

Gypsyamber D’Souza is a professor and David Dowdy an associate professor in Epidemiology at the Bloomberg School.

Can herd immunity stop COVID-19?

Whether or not COVID-19 can be conquered through herd immunity is an open question, according to experts.

In an April 1, 2021, article in the Boston Globe, Marc Lipsitch, professor of epidemiology and director of the Center for Communicable Disease Dynamics at Harvard T.H. Chan School of Public Health, was among experts who said that a lack of clear data on the virus and vaccines makes it hard to determine the possibility of reaching herd immunity, which could occur if enough people are vaccinated or otherwise immune to the virus.

There’s a simple math formula for calculating herd immunity. But the problem is that one of the figures needed for the formula is a disease’s infectiousness rate—and scientists aren’t sure what that rate is.

Early in the pandemic, scientists thought that each infectious person with COVID-19 would infect 2.5 to 3 other people—meaning that reaching herd immunity would require roughly two-thirds of a population to be immune, according to the formula. But that estimate may be off. Many early cases may have been missed because of limited early testing for COVID-19. And because people have changed their behavior over time, it may have masked the disease’s true infectiousness. “We were sort of stuck with bad data,” said Lipsitch.

Other factors further complicate the herd immunity calculation. One is the presence of highly infectious variants. Another is that it’s not known whether, and to what extent, vaccinated people can still transmit the disease to others.

If COVID-19 is more infectious than previously thought, the herd immunity threshold would be higher too. So, for instance, if each infectious person could infect four people, 75% of the population would need to be immune to stop the virus from spreading. If each person could infect five others, 80% would need to be immune if they could infect six others, 85% would need immunity.

Regardless of whether herd immunity can be achieved, it’s still important to vaccinate as many people as possible to slow COVID-19’s spread, according to the experts. “If we can turn this into a disease that is harmful, but to a smaller number of people, and on a smaller scale in terms of the hospital system, we will then decide as a society, as we do with the flu…to try to reduce it, but not to disrupt life on the same scale we’ve disrupted life so far to control it,” said Lipsitch. “We should not despair.”

Will Coronavirus Go Away Without a Vaccine? Here's What Experts Say

The COVID-19 pandemic will not suddenly come to an abrupt end on its own.


SARS-CoV-2, the coronavirus that causes COVID-19, hit the world hard over the course of the last few months. The world has seen its fair share of pandemics over the centuries, from the Black Plague to the Spanish Flu. More recently, there was the 2009 swine flu pandemic and the Ebola epidemic in 2014. However, the coronavirus has paused the world in a way that few living people have seen before. And as many people continue to shelter in place, some places are starting to reopen even without a coronavirus vaccine. Does that mean life can return to normal—and will the coronavirus go away without a vaccine?

Amesh Adalja, MD, an infectious-disease specialist and a senior scholar at the Johns Hopkins Center for Health Security, told Live Science that because the coronavirus has already "established itself in human populations," it cannot be eradicated without a vaccine. As the World Health Organization (WHO) explains, the eradication of a disease is "difficult and rarely achieved." And it never happens on its own, according to WHO: "There must be an available intervention to interrupt its transmission, available efficient diagnostic tools to detect cases that could lead to transmission, and humans must be the only reservoir."

So, what does that mean for everyone living through this pandemic? Physician scientist Steven Quay, MD, PhD, says he expects that the "coronavirus won't stop infecting humans for at least the next decade or so." He draws comparison to the severe acute respiratory syndrome (SARS) pandemic of 2003. However, there are key differences in how the coronavirus behind COVID-19 can be transmitted, which makes it harder to contain than SARS was.

"SARS came with great rapidity and with a lethal rate much higher than SARS-CoV-2, caused about 8,000 cases, and then has apparently disappeared," he says. "[But] with the high rate of both mild cases and asymptomatic patients in SARS-CoV-2, combined with virus shedding documented from the first day of infection and for as much as a month, I predict this coronavirus will infect every human on the planet in the next three years."


As for the possibility of a vaccine, Quay says that while there are several coronavirus vaccine candidates in development, there has never been a successful vaccine developed against a coronavirus before.

Alex Berezow, PhD, microbiologist and vice president of scientific communications at the American Council on Science and Health, confirms that there are currently a few different coronavirus vaccine candidates being tested. However, he says it will be some time before a vaccine becomes available, if one ever does.

"[I expect] no vaccine until 2021 or later," he says. "Vaccines must undergo extensive safety testing. The reason is because a bad vaccine can actually worsen the infection. We want to make sure the vaccine is safe before we inject it into millions or billions of people."

But with no vaccine currently available and the possibility that everyone can get infected, how does life return to some type of normal? Quay believes the answer is herd immunity, which can be developed through antibodies from previous infection. Herd immunity doesn't mean that the coronavirus disappears on its own, but instead, it would help us to become resistant to the virus. Without a vaccine, however, herd immunity is only achievable by many people getting sick.

And even though the virus could become less lethal over time as people develop some immunity and the spread slows down, Berezow says there are still some concerns. The most pressing is that scientists don't currently know how long immunity to the virus lasts. "Research shows that humans don't develop long-lasting immunity to coronaviruses, so it's likely that we'll be able to get infected again," he says. "The upside is that partial immunity is better than no immunity."

And for more on potential roadblocks to a coronavirus vaccine, discover The Shocking Problem That Could Prevent You From Getting the Coronavirus Vaccine.

It seems as though the goal posts for herd immunity keep changing. Why?

Experts estimate that between 60% and 90% of the U.S. population would need to be immune for there to be herd immunity. This wide range is because there are many moving parts that determine what is needed to achieve herd immunity.

Factors influencing whether the target is 60% or 90% include how well vaccination and prior infection prevent not only illness due to COVID-19, but also infection and transmission to others. Additional considerations include the heightened transmissibility of new variants of SARS-CoV-2 and the use of measures to interrupt transmission, including face masks and social distancing. Other important factors include the duration of immunity after vaccination or infection, and environmental factors such as seasonality, population sizes and density and heterogeneity within populations in immunity.

Immunity might not last forever

Calculations for herd immunity consider two sources of individual immunity — vaccines and natural infection. People who have been infected with SARS-CoV-2 seem to develop some immunity to the virus, but how long that lasts remains a question, Bansal says. Given what’s known about other coronaviruses and the preliminary evidence for SARS-CoV-2, it seems that infection-associated immunity wanes over time, so that needs to be factored in to calculations. “We’re still lacking conclusive data on waning immunity, but we do know it’s not zero and not 100,” Bansal says.

Modellers won’t be able to count everybody who’s been infected when calculating how close a population has come to the herd-immunity threshold. And they’ll have to account for the fact that the vaccines are not 100% effective. If infection-based immunity lasts only for something like months, that provides a tight deadline for delivering vaccines. It will also be important to understand how long vaccine-based immunity lasts, and whether boosters are necessary over time. For both these reasons, COVID-19 could become like the flu.

The Trouble With Herd Immunity And Covid-19 Vaccines

CARDIFF, WALES - DECEMBER 08: A woman is given a Pfizer-BioNTech Covid-19 vaccine at Cardiff and . [+] Vale Therapy Centre on December 8, 2020 in Cardiff, Wales. Wales joined the other UK nations in rolling out the covid-19 vaccine on Tuesday, a rare moment of coordination after months of disjointedness in the four nations' pandemic response. Wales introduced a 17-day "firebreak" lockdown in October and November to suppress the surge in covid-19 cases, but infections have continued to rise. (Photo by Matthew Horwood/Getty Images)

Now that an independent advisory panel has voted in favor of approving Pfizer’s two-dose Covid-19 vaccine, it likely won’t be long before the US Food and Drug Administration (FDA) clears it for emergency use. Within 24 hours of their decision, millions of doses will be en route to health workers and long-term care residents across the country, beginning a mass vaccination campaign that many hope will end in herd immunity.

A vaccine will make a critical addition to our defenses against Covid-19—this much is certain. But our ability to achieve vaccination-induced herd immunity is less so. While that shouldn’t stop us from trying, it also shouldn’t stop us from practicing and promoting safety guidelines that can actually contain the disease. If Covid-19 is a raging forest fire, and a vaccine the firefighter dispatched to quell it, tried-and-true prevention measures—social distancing, mask wearing, and rapid testing among them—are how we protect ourselves until the trucks come rolling in.

The World Health Organization estimates that 65 to 70 percent of a given population must be vaccinated to halt the spread of disease. Once that threshold is crossed, the Covid-19 virus will have too few human hosts to choose from, driving down transmission rates dramatically. The process of getting there is simple enough in theory, but laborious and time-consuming in practice, involving many factors that can be enumerated endlessly but boiled down to four.

The first factor involves properties intrinsic to both the vaccine and the virus. While the Pfizer vaccine has proven safe and effective at reducing disease in more than 95 percent of clinical trial participants, whether it prevents infection and transmission remains unknown. Likely it will, but until this is evident, we must continue to take great care in protecting ourselves and others from contracting disease, even post-vaccination.

The second factor is the duration of protection—in other words, how long the protection conferred by a vaccine will last. Several studies, though not all, suggest that natural immunity to the Covid-19 virus is quick to fade. Vaccine-induced immunity might do nature one better, but that isn’t always the case. The immune response precipitated by the influenza vaccine, for instance, dwindles in four to six months. Only time will tell whether our protection against Covid-19 is as short-lived.

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The third factor—social, rather than biological this time—is how many people take the vaccine. Due to a lack of data on how the Pfizer vaccine affects children and teens, Thursday’s FDA advisory panel deliberated its use in people 16 and over only. It may be that children below the age of 18, who make up about 23 percent of the population, aren’t cleared for vaccination for several months.

Until then, the onus is on adults—some of whom have their own reasons for abstaining. Whether their skepticism is fueled by fear-mongering from the anti-vax movement or, in the case of minority groups and in particular black Americans, a long history of malpractice in the name of medicine, the fact remains that 37 percent of adults in the United States would refuse to get vaccinated if the option were immediately available to them. Though trust, once lost, isn’t necessarily gone forever, it will take a concerted effort led by credible public figures and community leaders to undo damage that deep-seated.

The fourth and final factor is that the pandemic won’t be over in the United States until it’s over everywhere. For the rest of the world, mass vaccination will likely proceed at a much slower pace. If national public health interventions and global vaccine equity initiatives don’t pick up the slack, we can expect an influx of infections to continue streaming in from overseas, whether on the backs of travelers or packaging of frozen foods. Try as they might—and for the most part succeed—at keeping the virus at bay, China has traced hundreds of new infections to contaminated freight and other imported goods. While China has the wherewithal to quash even the smallest, most localized outbreaks with a barrage of testing, in many countries that slow drip is enough to trigger a flood.

Taking these factors into consideration, it becomes clear that vaccination-induced herd immunity isn’t a given. Whether it’s feasible, we probably won’t know for another couple of months. We do know that containing Covid-19 without a vaccine is. Countries like Australia, New Zealand, Thailand, and Taiwan, where strict lockdowns and basic prevention measures were rigorously enforced, have barely a handful of new cases to report daily, if any at all. Vaccines are just one tool among many, and to end the pandemic by this time next year, we need to give it all we got.

I am a scientist, businessman, author, and philanthropist. For nearly two decades, I was a professor at Harvard Medical School and Harvard School of Public Health where I

Vaccines don’t always prevent infection

Researchers had hoped to design safe COVID-19 vaccines that would prevent at least half of the people vaccinated from getting COVID-19 symptoms.

Fortunately, the vaccines have vastly outperformed expectations. For example, in 6.5 million residents of Israel, aged 16 years and older, the Pfizer–BioNTech mRNA COVID-19 vaccine was found to be 95.3% effective after both shots. Within two months, among the 4.7 million fully vaccinated, the detectable infections fell by 30-fold. Similarly in California and Texas, only 0.05% of fully vaccinated health care workers tested positive for COVID-19.

Vaccine developers often hope that, in addition to preventing illness, their vaccines will achieve “sterilizing immunity,” where the vaccination blocks the germ from even being able to get into the body at all. This sterilizing immunity means someone who’s vaccinated will neither catch the virus nor transmit it further. For a vaccine to be effective, though, it doesn’t need to prevent the germ from infecting an immunized person.

The Salk inactivated polio vaccine, for instance, does not completely stop polio virus from growing in the human gut. But it is extremely effective at preventing the crippling disease because it triggers antibodies that block the virus from infecting the brain and spinal cord. Good vaccines provide effective and durable training for the body’s immune system, so when it actually encounters the disease-causing pathogen, it’s ready to mount an optimum response.

When it comes to COVID-19, immunologists are still figuring out what they call the “correlates of protection,” factors that predict just how protected someone is against the coronavirus. Researchers believe that an optimum amount of “neutralizing antibodies,” the type that not only bind the virus but also prevent it from infecting, are sufficient to fend off repeat infections. Scientists are also still assessing the durability of immunity that the COVID-19 vaccines are providing and where in the body it’s working.

Why Did the WHO Alter Its Definition of “Herd Immunity?”

Herd Immunity. Even non-science types have a vague idea of what it means. Most of us realize it refers to the protection from viral infections when a large percentage of the population obtains immunity to it. A large immune population helps prevent the spread of the virus. But how is that immunity achieved?

According to the World Health Organization (WHO), the methods to obtain herd immunity used to be found on this web page. The page, titled Coronavirus Disease (Covid-19): Serology and dated 9 June, 2020, can be found on the Web Archive (Wayback Machine):

Acco r ding to the WHO, on June 9, 2020, herd immunity was defined as

“the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection.” (all emphasis mine)

An accurate and accepted definition, one that concurs with almost every other explanation on the internet and in every basic biology book I’ve ever seen.

Now compare this with the explanation currently on the same page as of 13 November, 2020. (

Now, the WHO states that herd immunity is:

a concept used for vaccination, in which a population can be protected from a certain virus if a threshold of vaccination is reached.

What happened to that other part? You know, the part about herd immunity being developed through previous infection?

Furthermore, they state that:

Herd immunity is achieved by protecting people from a virus, not by exposing them to it.”

Again, where’s the acknowledgement that herd immunity can be, and has been, established through previous infection?

The WHO not only chooses to ignore one of the main methods of achieving herd immunity, it also asserts some deceitful claims, if not flat out lies. For example:

Vaccines train our immune systems to develop antibodies, just as might happen when we are exposed to a disease but — crucially — vaccines work without making us sick.

Really? If you don’t personally know someone who has gotten sick from a vaccine, or have seen the headlines of negative reactions from the experimental Covid-19 vaccine, check out all the possible negative side effects listed in the inserts of all vaccines:

Vaccinated people are protected from getting the disease in question.

This is not always true. The makers of the experimental Covid-19 vaccines have stated it is unknown if the vaccine prevents transmission of the virus. Also, vaccinated people CAN get sick regardless of vaccination with any vaccine. (e.g.

Why would the WHO change the definition of herd immunity to completely ignore the other major half of it? Well, other than pushing the narrative that the experimental Covid-19 vaccine is the only way to save humankind from the Corona virus. Which, of course, raises an entirely new set of additional questions.

Do I need a vaccine if I’ve already had COVID-19?

On May 13, 2021, the Centers for Disease Control announced that in most cases, vaccinated adults in the U.S. could start going without masks, even indoors &mdash a long-awaited benchmark to signal a return to a more normal life. But many people still have lingering questions about the COVID-19 vaccines and whether or not they&rsquore needed, especially if you&rsquove already had COVID-19. As an infectious diseases expert and someone who contracted COVID-19 myself, I&rsquom here to share my insights.

I&rsquom young and healthy and I haven&rsquot caught COVID yet. Do I need to get a vaccine?

Yes, absolutely. The SARS-CoV-2 virus is still circulating in our communities, and we haven&rsquot reached herd-immunity levels of vaccination yet. Even if you are young and don&rsquot have any underlying health conditions that would put you at extra risk, the way individual people respond to COVID-19 is unpredictable &mdash that&rsquos part of what makes it so dangerous. In almost every case, I would recommend getting vaccinated. It protects not only you, but also those who are close to you and the people you love. If you don&rsquot want to get it for your own protection, get it for them.

Do I still need the vaccine if I&rsquove already had COVID-19?

Absolutely. While we know recovering from a COVID-19 infection means you will have circulating antibodies in your system, we are still learning about how the immune system handles the antibody response after a natural infection. We&rsquore not sure how protective the antibodies are from different kinds of infections &mdash such as an asymptomatic infection versus a symptomatic infection. With vaccination, we know that people with healthy immune systems are getting a great antibody response. So I would recommend vaccination even after a COVID-19 infection to get the best protection.

On top of that, if you live with people who are at higher risk of severe infection or may not develop a strong antibody level after vaccination, getting your own COVID-19 vaccination may make it less likely that you will transmit the virus to them.

When should I get vaccinated after having COVID-19?

The current guidance says that as long as you are no longer at risk of exposing other people to the virus, you can get your vaccine at any time. That means that once you are no longer in isolation and are no longer infectious, any time is fine. The exception is for people who received monoclonal antibodies as part of their COVID-19 treatment. The current recommendation is that these patients wait at least 90 days after their treatment to be vaccinated, because they will already have COVID-19 antibodies circulating in their system and we just don&rsquot know enough about the virus or its antibodies to know if this particular treatment could interfere with the vaccine&rsquos effectiveness.

Is it better to gain immunity through exposure to COVID-19 or through a vaccine?

With some viruses, such as chicken pox, being infected with the virus itself grants stronger immune protection than the chicken pox vaccine however, in those cases, you then have to deal with all the complications of having the virus. When it comes to COVID-19, it&rsquos really hard to know whether being exposed to the virus is more protective of future infection than the vaccine, simply because we don&rsquot know the SARS-CoV-2 virus well enough yet.

With natural immunity, which is the protection we get after being infected with a virus, the immune response can be variable. For example: the number of antibodies your body produces may depend on how much of the virus you&rsquore exposed to. And there is likely beneficial variation in the types of antibodies being produced. The vaccinations currently available in the U.S. have been shown to effectively stimulate antibodies against the virus&rsquo spike protein. New vaccines are being created that make antibodies to other parts of the virus as well. Both immunity from natural infection and vaccination stimulate a T-cell response that will hopefully provide you with protection from the virus for a longer time.

While it&rsquos possible some people may have a higher antibody response after a natural infection than they would after vaccination, we&rsquore still learning about this new virus, and we don&rsquot know how protective natural immunity really is, especially when there is such a continuum of different types of infections. We don&rsquot have clear data on how antibody responses from a mild infection compare to a severe infection, or how protective those antibody responses are.

On the other hand, we do know that the vaccine is very protective. In most people, getting vaccinated generates a lot of antibodies. So far, the vaccines appear to be incredibly effective, especially when it comes to preventing severe infections, hospitalizations and death.

Is there any extra risk if I get the vaccine after having had COVID-19?

There are a lot of anecdotal reports that many people who have had COVID-19 experience stronger side effects after their first vaccine dose, while most people who have never had COVID-19 have a stronger response after the second dose. But each person&rsquos experience is unique. Different people have different side effects and some people who haven&rsquot had COVID-19 report very strong side effects, too.

It&rsquos also important to note that it&rsquos possible many people who are being vaccinated were exposed to COVID-19 and had an asymptomatic infection without realizing it, which could contribute to the variation in side effects.

Personally, I found the side effects of my first vaccine to be pretty strong &mdash it felt like I had COVID-19 again &mdash but this time without the scary cough and shortness of breath. I had a high fever, chills and muscle aches, but it was not as overwhelming as I had feared. After a day or two, I was back to normal, and the side effects were certainly easier to manage than being sick with COVID-19. It was helpful to expect the side effects and to know my immune system was getting a boost. I was lucky to be able to plan to spend a day or two in bed. After my second vaccine, I just had a sore arm.

Can I still get COVID-19 after having the vaccine?

Yes, you can still get COVID-19 after getting the vaccine. In fact, we&rsquore sometimes seeing people pop up with reinfections. In the majority of cases, these are people who are being screened asymptomatically and just happen to be positive for the virus, or who show mild symptoms of the virus. The vaccine is intended to prevent severe infections and hospitalizations and it&rsquos doing an excellent job!

We can predict who might not have the best immune response to the vaccine &mdash these are usually people who have other health conditions affecting the strength of their immune system, such as organ transplants or cancer. These people are likely to have already been taking precautions to prevent illness even before the pandemic and will most benefit from continuing to follow other guidance on preventing COVID-19 even after their vaccination, such as mask wearing and social distancing.

We also think that the amount of virus a person is exposed to can influence the severity of infection. So even as masking guidance changes and people start gathering in larger crowds again, individuals should be aware of their own comfort levels and remember that even after vaccination, there is still some risk of possible infection.

I&rsquom still nervous!

I understand. I was nervous about getting my vaccine, too! After dealing with COVID-19, I was worried about the possible side effects, and the clinical trials hadn&rsquot really looked at whether there were any extra risks to getting the vaccine if a person already had the virus. But when my ticket came up, I decided to get my vaccine. I knew that it would give me more protection in the long term, and I had other personal reasons, too.

I wanted to feel comfortable seeing my parents again &mdash to spend time with my family and not worry about spreading the virus. I recently had the one-year anniversary of my COVID-19 diagnosis, and I get a little emotional to think about how far we&rsquove come. To think that we&rsquore able to start seeing people in person again, thanks to these vaccines. I am grateful to have had the opportunity to be vaccinated, and I hope that my patients will choose to be vaccinated, too.


  1. Nye

    looked and was disappointed ..........

  2. Willsn

    You are absolutely right. In it something is and it is good thought. It is ready to support you.

  3. Salmaran

    Strangely like that

  4. Amiti

    Sure version :)

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