Why You Should Get a COVID-19 Vaccine, Even If You Have Already Had Coronavirus


A few weeks ago, a message appeared in the corner of my screen. “What do you think of the people who have recently had COVID-19 getting the vaccine?” A friend of mine was eligible for a COVID-19 vaccine, but had recently overcome an infection with SARS-CoV-2. Every week, more people become eligible for vaccines, including millions of people who have already recovered from a coronavirus infection. Many wonder if they need the vaccine, especially people who have already been infected.

I study immune responses to respiratory infections, which is why I get a lot of these types of questions. A person can develop immunity, the ability to resist infection, by becoming infected with a virus or by receiving a vaccine. However, immune protection is not always the same. The strength of the immune response, the duration of protection, and the variation of the immune response between people is very different between vaccine immunity and natural immunity to SARS-CoV-2. COVID-19 vaccines offer safer and more reliable immunity than natural infection.

Immunity after infection is unpredictable

Immunity comes from the immune system’s ability to remember an infection. Using this immune memory, the body will know that it must fight if it encounters the disease again. Antibodies are proteins that can bind to a virus and prevent infection. T cells are cells that direct the elimination of infected cells and viruses that are already bound by antibodies. These two are some of the main players that contribute to immunity.

After a SARS-CoV-2 infection, a person’s antibody and T-cell responses can be strong enough to protect against reinfection. Research shows that 91% of people who develop antibodies to the coronavirus are unlikely to be infected again within six months, even after a mild infection. People who did not have symptoms during infection are also prone to developing immunity, although they tend to produce fewer antibodies than those who felt ill. So for some people, natural immunity can be strong and long-lasting.

The problem is that not everyone will develop immunity after a SARS-CoV-2 infection. Up to 9% of infected people do not have detectable antibodies and up to 7% of people do not have T cells that recognize the virus 30 days after infection.

For people who develop immunity, the strength and duration of protection can vary greatly. Up to 5% of people can lose their immune protection within a few months. Without a strong immune defense, these people are susceptible to reinfection by the coronavirus. Some have had second episodes of COVID-19 as early as a month after their first infection; and, although it is rare, some people have been hospitalized or have even died.

A person who is reinfected can also transmit the coronavirus even without feeling sick. This could put the person’s loved ones at risk.

And the variants? So far, there is no hard data on new coronavirus variants and natural immunity or reinfection, but it is certainly possible that the immunity from one infection is not as strong against infection with a different variant.

COVID-19 vaccines produce a strong immune response in terms of antibodies and T cells, like the T cell in this photo. Photo via the National Institutes of Allergy and Infectious Diseases / National Institutes of Health

Vaccination leads to reliable protection

COVID-19 vaccines generate both antibody and T-cell responses, but this is much stronger and more consistent than immunity against natural infection. One study found that four months after receiving their first dose of the Moderna vaccine, 100% of the people tested had antibodies to SARS-CoV-2. This is the longest period that has been studied so far. In a study that looked at the Pfizer and Moderna vaccines, antibody levels were also much higher in vaccinated people than in those who had recovered from the infection.

Even better, a study in Israel showed that the Pfizer vaccine blocked 90% of infections after both doses, even with one variant present in the population. And a decrease in infections means that people are less likely to transmit the virus to the people around them.

COVID-19 vaccines are not perfect, but they do produce strong antibody and T cell responses that offer a safer and more reliable means of protection than natural immunity.

Infection and vaccination together

To my friend’s message, I instantly replied that I should get the vaccine. After getting vaccinated, my friend might feel comfortable knowing that she has long-lasting and effective immunity and less chance of passing the coronavirus to her friends and family.

But more good news has emerged since I sent that message. A new study showed that vaccination after infection produces six times more antibodies than a vaccine alone. This is not to say that anyone should try to get infected before getting vaccinated; Immunity to the vaccine alone is strong enough to provide protection, and the dangers of a fight with COVID-19 far outweigh the benefits. But when my friend and many others who were already infected get vaccinated, they will be well protected.

Natural immunity to infection is far too unreliable against such a devastating virus. Today’s COVID-19 vaccines offer incredibly strong and consistent protection for the vast majority of people. So for anyone eligible, even those who have already had a SARS-CoV-2 infection, COVID-19 vaccines offer immense benefits.

This article has been republished from The Conversation under a Creative Commons license. Read the original article.
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