Question: An unvaccinated person I know recently got covid (didn’t end up in the hospital, luckily), and believes that he’s now immune to it as much as if he’d had the vaccine. Is he more protected now and surely he can be infected again?
Answer: Infection does trigger an immune response that generates antibodies and T cells, which will be protective (to some degree) against future infections. That said, reinfection is a risk. And recent research indicates that individuals who have been previously infected AND vaccinated have the most robust immune response and are the best protected against future infections. Your friend would do well to get vaccinated. Read on for more of the science:
- Infection-derived immunity (aka natural immunity) is more heterogeneous than vaccine-derived immunity, varying especially by age and by severity of infection. Restated, the degree of natural immunity varies dramatically from person to person, much more so than the degree of vaccine-derived immunity. (see Q&A of 6/15/21)
- Reinfection is increasingly common and unvaccinated individuals may be at increased risk of reinfection compared with vaccinated individuals. A study published by CDC’s MMWR in August examining reinfection risk in Kentucky found “Kentucky residents who were not vaccinated had 2.34 times the odds of reinfection compared with those who were fully vaccinated (odds ratio [OR] = 2.34; 95% confidence interval [CI] = 1.58–3.47). These findings suggest that among persons with previous SARS-CoV-2 infection, full vaccination provides additional protection against reinfection.”
- A study published just yesterday in Science Immunology finds that vaccination before or after SARS-CoV-2 infection results in substantial boost in neutralizing antibody (B-cell) response compared with vaccination alone. Restated, the hybrid immunity produced by vaccination followed by breakthrough infection and/or infection followed by vaccination is more robust than natural immunity or vaccine-derived immunity alone. Note: this study did not examine the impact of booster shots on immune response, which brings us to the next study…
- A study published earlier this month in Cell shows that the number of exposures to the spike protein– through infection or vaccination– is correlated with the strength of the antibody response (Figure 1). Again, infection followed by vaccination is far more protective than infection alone. And vaccine + booster appears as protective (antibody-wise) as hybrid immunity.
Figure 1. Three vaccine shots (e.g. vaccine + booster) are as protective as hybrid immunity (from Cell and EurekAlert)
