Calculate Your COVID-19 Immunity

A research paper published in the peer-review journal The Lancet Infectious Diseases presents a systematic review of the level of immunity derived from SARS-CoV-2 coronavirus infection and a mix of infection and COVID-19 vaccination, known as ‘hybrid immunity.’

The analysis published on January 18, 2023, shows that hybrid immunity provides higher protection.

Those with hybrid immunity had a 42% lower chance of being reinfected one year later.

Based on data from 26 studies, this analysis indicates that protection against severe COVID-19 and hospitalization remains high twelve months after developing hybrid immunity or having an infection compared to unvaccinated and uninfected individuals.

• The effectiveness of previous infection against hospital admission or severe disease was 74·6% (95% CI 63·1–83·5) at 12 months.
• The effectiveness of previous infection against reinfection waned to 24·7% (95% CI 16·4–35·5) at 12 months.
• The effectiveness of hybrid immunity against hospital admission or severe disease was 97·4% (95% CI 91·4–99·2) at 12 months with primary series vaccination and 95·3% (81·9–98·9) at six months with the first booster vaccination after the most recent infection or vaccination.
• Against reinfection, the effectiveness of hybrid immunity following primary series vaccination waned to 41·8% (95% CI 31·5–52·8) at 12 months, while the effectiveness of hybrid immunity following first booster vaccination waned to 46·5% (36·0–57·3) at six months.

In summary, these researchers wrote that individuals with hybrid immunity had the highest magnitude and durability of protection against all outcomes, emphasizing the importance of vaccinating previously infected individuals.

Furthermore, in countries where only S-protein antigen vaccines were used, it might be possible to classify individuals as previously infected with an anti-N antibody test and use this to modify recommendations for boosters.

Our findings are in line with a recent study that reported higher quality and magnitude of immune responses (antibodies and B cells) with a longer interval between infection and booster vaccination (>180 days).

It might therefore be reasonable for individuals with a previous infection and complete primary series vaccination to delay subsequent doses of vaccination by six months while maintaining high levels of protection against severe disease.

And this systematic review had several potential limitations. First, the patterns of declining protection observed in this study might be explained by waning immunity; however, these results could also be partly attributable to unmeasured biases.

These findings are the product of a collaboration between the World Health Organization, Unity Studies, and SeroTracker. These researchers disclosed no industry conflicts of interest.