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.

Protection by a Fourth Dose of BNT162b2 against Omicron in Israel – New England Journal of Medicine

Commentary: Mixed Bag for Fourth Dose of Pfizer Vaccine vs Omicron— Real-world data show less infection and severity, but long-term benefit less clear – MedPage Today (free registration required)

Related:

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

Just published @NEJM
4th dose vaccine protection in >620,000 people vs 3-doses in >620,000, all age 60+, Omicron wave, Israel
—4-fold lower rate of severe disease, no waning at 6 weeks
—2-fold lower rate of infection, rapidly wanedhttps://t.co/g8uGMXGHD6 pic.twitter.com/D7WHywTI1j

— Eric Topol (@EricTopol) April 5, 2022