How effective is the Moderna vaccine after 5 months?

Now, all adults over 18 can claim a booster of an anti-Covid-19 vaccine at MRNA five months after their last dose, or infection. This recall is intended to counter the gradual decrease vaccine immunity. But what remains five months after a first complete vaccination schedule, just before the booster dose? Scientists from Kaiser Permanente, a health center based in California, estimated the protection conferred by the Moderna vaccine, just five months after the second and last dose. They followed more than 600,000 people, vaccinated or not, in December 2020 and June 2021. From this real-life data, they estimated the effectiveness of Moderna’s vaccine against infection, hospitalizations and deaths.

The effectiveness of the Moderna vaccine, five months after the second dose

A total of 352,878 people vaccinated with the two doses of Moderna participated in the study. Each of them was associated with one of the 352,878 unvaccinated people with a similar socio-demographic profile. For five months, scientists followed Covid-19 cases in both groups. Among the vaccinated, 289 cases of Covid-19 over the period of the experiment were counted, against 1,144 in the group of unvaccinated. Only thirteen people in the vaccinated group had to be hospitalized, compared to 182 in the unvaccinated group. Finally, there is one death in the vaccinated group, against 25 in the unvaccinated at the end of five months.

From these observations, the effectiveness of the Moderna vaccine after five months against infection, hospitalizations and deaths could be calculated. It is 87.4% against infections, 95.8% against hospitalizations and 97.9% against deaths. During this time, several variants infected the participants. the Alpha variant was still in the majority (41.6%), followed by the Epsilon variant (17.5%), Delta (11.5%) and Gamma (9.1%). The efficiency calculated by the scientists of the Kaiser Permanente is not specific to a specific variant. However, the Delta variant is famous for resist vaccines. The same could happen with the Omicron variant.

Less effective vaccines against the Omicron variant

The Moderna executive told the Financial Times that existing vaccines will be less effective against the variant Omicron barely emerging, and that it will take several months to design a new formula. For the moment, no scientific data solid does not confirm the ability of the Omicron variant to escape vaccine immunity. Scientists from Kaiser Permanente will continue this study, since these results are only a foretaste of their final conclusion that they will deliver at the end of the five years that will last for the follow-up of the participants.