If you had COVID-19, you may wonder if you now have natural immunity to the coronavirus. And if so, how does that compare to protection offered by the COVID-19 vaccinations?

Lisa Maragakis, M.D., M.P.H., senior director of infection prevention, and Gabor Kelen, M.D., director of the Johns Hopkins Office of Critical Event Preparedness and Response, help you understand natural immunity and why getting a coronavirus vaccine is recommended, even if you’ve already had COVID-19.

What is immunity?

Immunity is your body’s ability to protect you from getting sick when you are exposed to an infectious agent (“germ”) such as a bacterium, virus, parasite or fungus.

Immunity is a complex process that involves a lot of moving parts. Your body produces a variety of different cells that fight invading germs. Some of these release special proteins called antibodies into your blood stream. These antibody producing cells can “remember” a particular germ so they can detect its presence if it returns and produce antibodies to stop it.

What is natural immunity?

Natural immunity is the antibody protection your body creates against a germ once you’ve been infected with it. Natural immunity varies according to the person and the germ. For example, people who have had the measles are not likely to get it again, but this is not the case for every disease. A mild case of an illness may not result in strong natural immunity. New studies show that natural immunity to the coronavirus weakens (wanes) over time, and does so faster than immunity provided by COVID-19 vaccination.

What is vaccine-induced immunity for COVID-19?

Vaccine-induced immunity is what we get by being fully vaccinated with an approved or authorized COVID-19 vaccine. Research indicates that the protection from the vaccines may wane over time so additional doses (boosters) are now authorized for certain populations. These boosters can extend the powerful protection offered by the COVID-19 vaccines.

If I have natural immunity do I still need a COVID vaccine?

Yes, the COVID-19 vaccines are recommended, even if you had COVID-19. At present, evidence from Johns Hopkins Medicine and the U.S. Centers for Disease Control and Prevention (CDC) supports getting a COVID-19 vaccine as the best protection against getting COVID-19, whether you have already had the virus or not.

Here are recent research studies that support getting vaccinated even if you have already had COVID-19:

Vaccines add protection.

• The U.S. Centers for Disease Control and Prevention (CDC) released a report on Oct. 29, 2021, that says getting vaccinated for the coronavirus when you’ve already had COVID-19 significantly enhances your immune protection and further reduces your risk of reinfection.
• A study published in August 2021 indicates that if you had COVID-19 before and are not vaccinated, your risk of getting re-infected is more than two times higher than for those who got vaccinated after having COVID-19.
• Another study published on Nov. 5, 2021, by the U.S. Centers for Disease Control and Prevention (CDC) looked at adults hospitalized for COVID-like sickness between January and September 2021. This study found that the chances of these adults testing positive for COVID-19 were 5.49 times higher in unvaccinated people who had COVID-19 in the past than they were for those who had been vaccinated for COVID and had not had an infection before.
• A study from the CDC in September 2021 showed that roughly one-third of those with COVID-19 cases in the study had no apparent natural immunity.

Immunity varies for individuals: Immune response can differ in people who get COVID-19 and recover from the illness. The FDA-authorized and approved vaccines have been given to almost 200 million people in the U.S. alone, and have strong data supporting their effectiveness.

Delta variant and future coronavirus variants: Hospitalizations of people with severe COVID-19 soared over the late summer and into fall as the delta variant moved across the country. People infected with earlier versions of the coronavirus and who haven’t been vaccinated might be more vulnerable to new mutations of the coronavirus such as those found in the delta variant. To date, the authorized vaccines provide protection from serious disease or death due to all currently circulating coronavirus variants.

Should I hold off getting a COVID vaccine to see if there is new research on natural immunity?

Holding off on getting vaccinated for COVID-19 is not a good idea. Here’s why:

1. Getting COVID-19 is very risky and can result in long-term disease, lasting organ damage, hospitalization or even death.
2. Even if your own infection is mild, you can spread it to others who may have severe illness and death.
3. The authorized and approved vaccines are safe and highly effective against severe illness or death due to COVID.
4. Risks of COVID-19 vaccine side effects are extremely low.

For the reasons above, the CDC recommends and Johns Hopkins Medicine agrees that all eligible people get vaccinated with any of the three FDA-approved or authorized COVID-19 vaccines, including those who have already had COVID-19.

Johns Hopkins Research on Natural Immunity for COVID-19 and COVID Vaccines

Johns Hopkins has conducted a large study on natural immunity that shows antibody levels against COVID-19 coronavirus stay higher for a longer time in people who were infected by the virus and then were fully vaccinated with mRNA COVID-19 vaccines compared with those who only got immunized. (The results of the study were published in a letter to the Journal of the American Medical Association on Nov. 1, 2021.)

The data show that one month after they got their second shot, participants who had had COVID-19 more than 90 days before their first shot had adjusted antibody levels higher than those who had been exposed to the coronavirus more recently than 90 days. Three months after the second coronavirus vaccine, the antibody levels were even higher: 13% higher than those who were exposed to the virus less than or equal to the 90-day mark.

These study results suggest that natural immunity may increase the protection of the shots when there is a longer time period between having COVID-19 and getting vaccinated.