A nationwide observational analysis in Israel showed a fourth dose of the Pfizer vaccine may reduce the short-term risk of Covid-19–related outcomes.

Fourth Dose of BNT162b2 mRNA Covid-19 Vaccine in a Nationwide Setting – New England Journal of Medicine

Editorial: Covid-19 Boosters — Where from Here?

Related:

COVID-19: Joint statement from ECDC and EMA on the administration of a fourth dose of mRNA vaccines.

Observational study suggests a fourth dose of the Pfizer vaccine provided additional protection against severe disease in patients 60 years of age or older during the Omicron wave in Israel.

Perspective: The evidence on 4th doses of covid vaccines & the thorny question of age thresholds.

U.S. approves second Covid-19 booster for people 50 and older and immunocompromised individuals.

[Preprint] Retrospective cohort study: second booster vaccine and Covid-19 mortality in adults 60 to 100 years old.

Among health care workers, a fourth dose vaccine effectiveness against any SARS-CoV-2 Omicron variant infection was 30% for the Pfizer–BioNTech and 11% for the Moderna.

[Preprint] Fourth dose of COVID vaccine offers only slight boost against Omicron infection.

Covid-19: Fourth vaccine doses—who needs them and why?

[Not published yet] Study in Israel finds fourth COVID booster has limited efficacy.

Commentary on Twitter

In Israel, a fourth dose of BNT162b2 vaccine effective in reducing the short-term risk of Covid-19–related outcomes among those who had received a third dose at least 4 mos earlier. https://t.co/WtHiR9WbLW pic.twitter.com/yzWRLlgHUi

— NEJM (@NEJM) April 13, 2022