Does Natural Immunity Protect Against the SARS-CoV-2 Variants, or Do I Still Need the Vaccine?

While antibodies from a COVID-19 infection may offer some degree of protection against another future infection, those who have already had the virus may still be vulnerable to the disease. Many of the variants tend to be more contagious and spread more easily than the original strain of SARS-CoV-2, the virus that causes COVID-19. So, the natural immunity that you may get from having been infected may not keep you from getting sick again.

A Centers for Disease Control and Prevention (CDC) study published in 2021 compared reinfection rates of people who had previously had COVID-19 and found that unvaccinated individuals were more than twice as likely to be reinfected than fully vaccinated individuals.

For that reason, experts don't recommend relying on natural immunity alone to prevent a COVID-19 infection. Here's what you need to know about how to protect yourself and others from the COVID-19 variants.

Get Vaccinated Even If You've Had the Virus

All infections provide some degree of protection from future sickness by producing antibodies, proteins that your immune system produces to protect against foreign substances. "When you get infected with a virus, you make an immune response against it, just like you do with a vaccine," said Seema S. Lakdawala, PhD, an associate professor of microbiology and molecular genetics at the University of Pittsburgh School of Medicine. According to Dr. Lakdawala, the immune system creates antibodies and T-cells to the specific virus, which respond when they "see" that virus again.

That immune response may help fight off a future infection, said Amesh A. Adalja, MD, a senior scholar at Johns Hopkins Bloomberg School of Public Health's Center for Health Security. The problem is that SARS-CoV-2, the virus that causes COVID-19, continues to mutate, so that original protection may not be effective against new mutations. "When you get infected, you become immune to viruses that are similar," explained Dr. Lakdawala. "But the whole point of viruses is to continue to spread, so they evolve and change."

For example, Taylor Heald-Sargent, MD, an assistant professor of pediatrics specializing in infectious diseases at Northwestern University Feinberg School of Medicine, explained that if you had COVID-19 during the initial outbreak in spring 2020, it's more likely than not that your antibodies didn't measure up against the Delta strain.

While one person may have some degree of immunity to one of the variants from a previous infection, the level of protection can drastically vary between individuals, Dr. Heald-Sargent said. For example, she said, an immunocompromised person may mount a weaker immune response than other individuals. Those who had milder forms of COVID-19 may also have weaker antibodies, said Joshua LaBaer, PhD, MD, executive director of the Biodesign Institute at Arizona State University.

But no matter the severity, a past COVID-19 diagnosis isn't a guarantee of protection: A study conducted by the University of Oxford found that people with weaker immune responses from a previous infection could be at a higher risk of contracting one of the newer variants of COVID-19. "We (saw) lots of examples of people who had the infection in the past and who got reinfected despite that, both with the Delta variant and previous strains," said Dr. LaBaer.

What Should I Know About Antibodies, Vaccines, and the COVID-19 Variants?

The CDC recommends vaccination for all eligible individuals, including those who have already had COVID-19. Compared to natural immunity, Dr. Adalja said immunity from vaccination is stronger, more robust, and more predictable—making it the best route for protecting against severe illness from the variants.

While an infection creates antibodies against all the proteins in a particular viral strain, vaccination is more focused on neutralizing the most important protein. "The spike protein, which binds to receptors to get inside a person's cells, is the most important protein for a wide variety of strains," said Dr. Lakdawala. Antibodies against the virus' spike proteins neutralize the entire virus, she explained, which can prevent it from entering the cells and making you sick.

Vaccines also provide more antibodies to fight off a new infection. Dr. LaBaer said while people who have been infected may have antibodies in their blood, those antibodies increase considerably upon vaccination.

Due to the increased antibodies, when the vaccine protection starts to wear off, people might be protected longer. "The vaccine elicits many more antibodies than a natural infection, so as the vaccine declines, the protection lasts longer than it would from a natural infection," said Dr. Heald-Sargent.

Though vaccination efficacy may drop after a time, putting vaccinated individuals at greater risk of breakthrough infections, they are doing their job: protecting against severe disease, hospitalization, and death. A 2022 study in The Lancet shows that vaccines were as effective against the Omicron BA.2 variant as they were against the BA.1 variant.

Because of a drop in vaccination efficacy over time, the CDC recommends that anyone who is eligible should get the COVID-19 vaccine boosters. In fact, if you've had coronavirus and are up-to-date on your vaccines, you may be the most protected compared to those with just natural immunity or just the vaccination. A December 2021 study published by the American Society for Microbiology found "that the combination of infection and vaccination drove the production of enhanced antibodies to reach a maximal level of potency."

Vaccinated or not, experts encourage continued masking and physical distancing in public spaces, especially when your community level of COVID-19 is high. "Even if you're vaccinated, you can still have an infection," said Dr. Heald-Sargent. "It might not make you sick, but you could still transmit it to someone else."

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up to date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.