Protection of BNT162b2 Vaccine Booster against Covid-19 in Israel | NEJM
▻https://www.nejm.org/doi/full/10.1056/NEJMoa2114255
At least 12 days after the booster dose, the rate of confirmed infection was lower in the booster group than in the nonbooster group by a factor of 11.3 (95% confidence interval [CI], 10.4 to 12.3); the rate of severe illness was lower by a factor of 19.5 (95% CI, 12.9 to 29.5). In a secondary analysis, the rate of confirmed infection at least 12 days after vaccination was lower than the rate after 4 to 6 days by a factor of 5.4 (95% CI, 4.8 to 6.1).
Si je comprends bien, selon cette étude, le rappel réduit le risque de contamination par 11 (pas seulement risque de forme sévère ou de décès : ça parle bien de la « simple » contamination).
Ce qui, selon les auteurs, rétablirait une protection de 95% contre la contamination.
In our study, we found that a booster dose of the BNT162b2 vaccine reduced the rates of both confirmed infection and severe Covid-19 illness in a large Israeli population of participants who were 60 years of age or older. Our findings can be understood through the following example. Suppose, first, that the combined effect of waning immunity and the increased prevalence of the delta variant decreases the efficacy of a vaccine that had been administered 6 months earlier to approximately 50% relative to the susceptibility in an unvaccinated person, as recent reports have suggested.2,16,17 Then suppose that, as suggested by our results, the booster dose reduces the rate of infection for such vaccine recipients by a factor of 10. This would mean that the susceptibility of a person who receives a booster dose would decrease to approximately 5% (i.e., 50% divided by 10) relative to that in an unvaccinated person and would bring the vaccine efficacy among booster recipients to approximately 95%, a value similar to the original vaccine efficacy reported against the alpha variant.