There has been much debate about the efficacy of vaccine-induced immunity vs. infection-induced (or “natural”) immunity. While it’s true that getting any virus or infection — in this context, specifically COVID-19 — will cause your body to produce antibodies that can help you fight off later infections, some people are under the impression that natural immunity is more effective than vaccine immunity. However, this is not the case.
Proponents of natural immunity cite recent studies out of California/New York and Israel. Despite headlines reporting previous infection offers more protection than vaccination, both studies come with an important caveat: Natural immunity was only more effective against the delta variant — not against the original COVID-19 strain or the alpha variant, and both studies were published before omicron became the dominant strain. The California/New York study says, “Before [d]elta … case rates were higher among persons who survived a previous infection than persons who were vaccinated alone.”
There is some benefit to natural immunity, of that there is no doubt. During the first waves of COVID, the consensus was that vaccine immunity lasted longer than natural immunity. But one study suggests that natural infection may provide a more robust immune response against later infections, though it does not discount the effectiveness of vaccines.
Michel C. Nussenzweig, with The Rockefeller University, published a study (prior to omicron) that found infection creates memory B cells that continue to evolve longer than memory B cells created by vaccination. According to Arizona State’s “Ask a Biologist,” memory B cells “remember the virus or bacteria they just fought” and help produce antibodies to fight subsequent infections. The study also says, “While individual memory antibodies selected over time by natural infection have greater potency and breadth than antibodies elicited by vaccination, the overall neutralizing potency of plasma is greater following vaccination.”
Several studies, including the two mentioned at the beginning of this editorial, found that the best protection — at least against delta — was a combination of natural immunity plus at least one dose of mRNA vaccine. That’s why it’s important for people who have been previously infected to still get vaccinated.
But there are varying levels of risk associated with acquiring natural immunity — so much so that even Nussenzweig said vaccination is the safer option, and it still “protects against the risk of serious illness or death from infection.” The CDC and Johns Hopkins encourage vaccination over infection, and so do a multitude of other health institutions, including UCLA Health and Children’s Hospital of Philadelphia.
Virologist Sabra Klein, with Johns Hopkins, said natural immunity is highly dependent upon severity of infection: Someone who had severe COVID but survived will have much greater immunity than someone who had a mild or asymptomatic case. If you get infected instead of vaccinated, you “roll the dice” — you may be fine, you may get “long COVID” or you may die.
While all the studies mentioned above looked at the alpha and delta variants, omicron has proven to be its own unique creature. A study published in late December 2021, by David Ho with Columbia University, concluded neither natural nor vaccine immunity were as effective against omicron as they were against early waves and variants. However, antibodies created through vaccination did a better job fighting omicron than antibodies from previous infection. People who are vaccinated and boosted had the best antibody responses to omicron.
While there is some benefit to natural immunity, the safest option — both in terms of now and later — is to get your vaccines, and, when it’s time, get the booster shot.
