A case-control study published in The Lancet Respiratory Medicine revealed that 3 doses of BNT162b2 offered promising safety and high protection against admission to emergency department and hospital because of both omicron and delta variants in the first three months post-vaccination. But, three months after receipt of a third dose, waning was apparent against COVID-19 outcomes due to omicron variant, including hospitalization.

Sara Y Tartof et al. aimed to determine the durability and efficacy of 2 and 3 doses of BNT162b2 vaccine against admission to emergency department and hospital because of the delta and omicron variants. Overall, 11123 hospital or emergency department admissions were analyzed. Calculation of efficacy of vaccine was done in people diagnosed with acute respiratory infection and who were COVID-19 positive (18 years and older) admitted to hospital or an emergency department. Utilizing odds ratios from adjusted logistic regression models, estimation of adjusted vaccine efficacy was done.

Notably, efficacy of 2 doses of BNT162b2 vaccine against omicron variant was found to be 31% against admission to emergency department and 41% against admission to hospital at 9 months or longer post second dose. Following 3 doses, efficacy of BNT162b2 against admission to hospital because of omicron variant was 85% at less than three months. However, it reduced to 55% at 3 months or more.

Regarding admission to emergency department, efficacy of 3 doses of BNT162b2 against the omicron variant was found to be 77% at less than three months. However, at three months or more, it dropped to 53%. The trends in declining against coronavirus outcomes because of delta variant were usually comparable, but with greater efficacy estimates at every timepoint than those observed for omicron variant.

Hence, additional doses of coronavirus vaccines may be required in maintaining a high level of protection against severe COVD-19 infection due to the omicron variant or subsequent variants.