Protection against Omicron BA.1/BA.2 severe disease 0-7 months after BNT162b2 booster.

Area of Science:

• Immunology
• Vaccinology
• Epidemiology

Background:

• Waning immunity after two doses of the BNT162b2 vaccine necessitated booster doses.
• Limited data existed on third-dose effectiveness against severe disease from Omicron (BA.1/BA.2) variants.
• Previous studies indicated reduced and rapidly waning protection against Omicron infection after a third dose.

Purpose of the Study:

• To estimate the durability of immunity against severe coronavirus disease 2019 (COVID-19) up to seven months post-booster.
• To assess the comparative effectiveness of two, three, and four doses of the BNT162b2 vaccine against severe Omicron disease in older adults.

Main Methods:

• Retrospective cohort study analyzing severe COVID-19 disease rates in individuals aged 60 and above.
• Comparison of disease rates between individuals who received two doses (at least 4 months prior), three doses (stratified by time since vaccination), and four doses.
• Focus on severe SARS-CoV-2 disease outcomes specifically related to Omicron (BA.1/BA.2) variants.

Main Results:

• Protection against severe Omicron disease conferred by the third BNT162b2 vaccine dose remained stable over a seven-month period.
• A fourth dose demonstrated significantly enhanced protection, resulting in approximately a threefold lower rate of severe disease compared to the three-dose cohort.
• The study provides crucial evidence on the long-term effectiveness of booster vaccination against severe outcomes of Omicron subvariants.

Conclusions:

• The third BNT162b2 vaccine dose provides sustained protection against severe Omicron (BA.1/BA.2) disease for at least seven months.
• A fourth dose offers additional significant protection against severe disease, highlighting its importance in maintaining immunity in older populations.
• These findings support the strategy of booster vaccinations, including fourth doses, for robust protection against severe COVID-19 outcomes.