People that had SARS-CoV-2 infections may think that they have “natural immunity” and are protected from getting re-infected from this COVID-19 virus. But there are 2 new studies showing evidence that vaccination generates a more vigorous B and T cell (immune memory cells) response than does natural infection. It shows that vaccination is particularly stronger in people with previous SARS-CoV-2 infections.
Researchers evaluated people who were vaccinated with the mRNA vaccine after natural infection and people who were vaccinated but had no prior infection. Memory B cells against SARS CoV-2 were 5-10-fold higher when vaccination followed natural infection than after natural infection or vaccination alone. The most surprising result was that in people who were vaccinated after natural infections, neutralizing antibodies against the beta variant were higher. They were 25 times higher than after vaccines alone and 100 times higher than after natural infection alone. This was amazing since natural infections were almost never with the beta variant and that vaccines don’t target the beta variant spike protein.
Other studies as well have shown similar results. A study in the CDC (Centers for Disease Control and Prevention) Morbidity and Mortality Weekly report shows 2.3 times the number of reinfections with natural immunity compared to breakthrough infections in those who are vaccinated. It is unclear how effective natural infection is against other variants, particularly the Delta variant. This new variant, as well as the lambda variant, may weaken the protection provided by having been previously infected by SARS-CoV-2.
People who have had COVID-19 are advised to be vaccinated. It will very likely offer better protection against symptomatic reinfections, even with the Delta and future variants.
References: Diamond, F. Kavanagh, K. Get vaccinated even if you’ve gotten COVID-19, study suggests. Infection Control Today 2021, Aug 8.
Stamatatos, L et al. mRNA vaccination boosts cross-variant neutralizing antibodies elicited by SARS-CoV-2 infection. Science 2021 Mar 25; 372: 1413.