COVID-19 Vaccine Effectiveness Against Omicron Infection and Hospitalization. 3/3/2023. Piché-Renaud PP. Pediatrics.

Canadian investigators examined Ontario databases for BNT162b2 vaccine effectiveness (VE) against Omicron in children ages 5-11 (6284 test-positive cases and 8389 test-negative controls).  VE was estimated by time since the latest dose vs. unvaccinated children and evaluated VE by dosing intervals. Symptomatic infection declined 24% (2-4 weeks after a first dose) and 66% (1-4 weeks after 2 doses). An extended 8-week dosing interval was associated with higher effectiveness against symptomatic infection for the first 3 months after vaccination. Severe outcomes were reduced 94% (7 to 29 days after 2 doses) and declined to 57% after 120 days. Conclusion: 2 doses of BNT162b2 provide moderate protection against symptomatic Omicron within 4 months of vaccination and good protection against severe outcomes. Protection wanes faster for infection than severe outcomes. Longer dosing intervals confer higher protection against symptomatic infection, but by 90 days, protection decreases and becomes like shorter dosing intervals.  VE vs Omicron declined faster vs. former variants.

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