Immune Response From mRNA COVID-19 Vaccines Is More Robust Than Natural Infection
Antibody levels induced by mRNA COVID-19 vaccines are much higher than those induced by natural infection and confer cross-reactivity that could be effective against new variants,
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“Ab levels induced by the vaccine are much higher than levels induced by natural exposure and infection,” Felgner said. “The vaccine also induces cross reactive Abs against other novel CoV strains that are not induced by natural exposure and infection. This offers hope that the vaccine will be effective against emerging virus variants that are circulating around the world.”
The vaccines induced robust reactivity levels, including antibodies against the full-length spike protein, S1 and S2 subunits, and the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, which binds to the angiotensin-converting enzyme 2 (ACE2) receptor on host cells. Cross-reactive antibodies between the spike protein and RBD induced by the vaccine could possibly provide protection against emerging variants.
This differs from the response from natural infection, which had weak antibody levels against RBD but produced the highest levels of antibodies against nucleocapsid protein (NP) antigens. Anti-nucleocapsid antibodies weren’t affected by the vaccines and could indicate prior natural exposure.
After the second dose of the vaccine, antibody titers were up to 10 times higher than those of patients who had recovered from natural COVID-19 infection, suggesting that even those with prior exposure could benefit from vaccination.
The study also found that people who have had prior exposure to SARS-CoV-2 had a stronger immune response to the vaccine, developing antibody levels faster than those who hadn’t been exposed to the virus.