Sara Y. Tartof et al.: BNT162b2 vaccine effectiveness against SARS-CoV-2 omicron BA.4 and BA.5, in: The Lancet. Infectious Diseases Volume 22 (December 2022) Issue 12, pp. 1663-1665, online in: https://doi.org/10.1016/S1473-3099(22)00692-2.
Following their first detection in South Africa in late 2021, the SARS-CoV-2 omicron subvariants BA.4 and BA.5 have become the predominant subavariants. In their study, the authors evaluated the efficacy of the Pfizer-BioNTech vaccine BNT162b2 (Comirnaty) against BA.4/5, concluding that two doses of the vaccine provided only modest protection against all measured BA.4/5 illnesses, including hospitalizations. Booster vaccination (third or fourth dose) did provide protection against BA.4/5, but this protection likely wanes after 3 months (for milder episodes such as outpatient urgent care or emergency department stays) or after about 6 months (for BA.4/5-related hospitalizations).