Immunity

Michel Nussenzweig and colleagues investigated the immunity in a group of recovered adult patients (n=63) that visited for a 12-month follow-up. The participants were aged between 26 to 73 years and had had relatively mild infections, with only 10% been hospitalized for their illness during the prior year. 41% of these patients had received at least 1 dose of an mRNA vaccine at an average of 40 days before the 12-month follow-up visit. All were SARS-CoV-2 negative at the follow-up.

This made Nussenzweig’s team learn that antibodies against SARS-CoV-2 continue to evolve up to a year after infection and vaccines further improve the immune response.

When compared with unvaccinated participants, those receiving at least one dose showed higher plasma anti- receptor-binding domain (RBD) antibodies and about 50 times increase in neutralizing activity. 

Thus they demonstrated that vaccination boosts the memory antibodies, developed after infection, producing an “outstanding response.” 

This study group demonstrated neutralizing antibody levels against the variants that even surpassed the levels observed against the wild-type virus in infected or fully vaccinated individuals in other studies. 

Two more studies published by the researchers of North America and the UK, in Science, demonstrated that a single dose of an mRNA vaccine substantially enhances the immune response to SARS-CoV-2 variants among patients with prior infection. This phenomenon is been termed a “hybrid immunity.”

Another yet recent study published by researchers from France, in Nature, analyzed recovered patients’ immunity against the highly transmissible Delta variant. They described, the unvaccinated health care workers had less protection against the delta and beta variants compared with an alpha after a year from the recovery of mild COVID-19. This group demonstrated neutralizing antibodies against alpha in 88% of the individuals contrasting only 47% of individuals neutralizing delta. Interestingly, recovered health care workers receiving 1 dose of any SARS-CoV-2 vaccine demonstrated a marked increase in neutralizing antibody levels against all 3 of these variants compared with their unvaccinated peers.

Nussenzweig further believes that uninfected, immunized people may need boosters at some point, but it’s not known how soon that will be. 

Source- Abbasi J. Study Suggests Lasting Immunity After COVID-19, With a Big Boost From Vaccination. JAMA. 2021;326(5):376-377. doi:10.1001/jama.2021.11717