Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, January – September 2021
Abstract
Background
SARS-CoV-2 vaccines show high effectiveness against infection and (severe) disease. However, few studies estimate population level vaccine effectiveness against multiple COVID-19 outcomes, by age and including homologous and heterologous vaccine regimens.
Methods
Using Cox proportional hazard models on data from 4 293 544 individuals (99% of Norwegian adults), we estimated overall, age-, and product-specific vaccine effectiveness against SARS-CoV-2 infection, hospitalisation, ICU admission and death in Norway, using data from national registries. Vaccine status was included as time-dependent variable and we adjusted for sex, pre-existing medical conditions, country of birth, county of residence, and crowded living conditions.
Findings
Adjusted vaccine effectiveness among fully vaccinated is 72·1% (71·2–73·0) against SARS-CoV-2 infection, 92·9% (91·2–94·2) against hospitalisation, 95·5% (92·6–97·2) against ICU admission, and 88·0% (82·5–91·8) against death. Among partially vaccinated, the effectiveness is 24·3% (22·3–26·2) against infection and 82·7% (77·7–86·6) against hospitalisation. Vaccine effectiveness against infection is 84·7% (83·1-86·1) for heterologous mRNA vaccine regimens, 78·3% (76·8-79·7) for Spikevax (Moderna; mRNA-1273), 69·7% (68·6-70·8) for Comirnaty (Pfizer/BioNTech; BNT162b2), and 60·7% (57·5-63·6) for Vaxzevria (AstraZeneca; ChAdOx nCoV-19; AZD1222) with a mRNA dose among fully vaccinated.
Interpretation
We demonstrate good protection against SARS-CoV-2 infection and severe disease in fully vaccinated, including heterologous vaccine regimens, which could facilitate rapid immunization. Partially vaccinated were less likely to get severe disease than unvaccinated, though protection against infection was not as high, which could be essential in making vaccine prioritisation policies especially when availability is limited.
Funding
Norwegian Institute of Public Health, Helse Bergen Health Trust
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