Study registration: *
Publication Seppala E, Euro Surveill, 2021
Dates: 2020-12-27 to 2021-08-15
Funding: No specific funding (No specific funding received. The study was performed as part of routine work at the Norwegian Institute of Public Health.)
Conflict of interest: no COI (None declared.)

Methods

Study design:Cohort
Description of participants: All adults aged 18 years or older with no prior SARS-CoV-2 infection with a national identification number registered in multiple centres in Norway
Inclusion criteria:
  • All adults aged 18 years or older
  • with a national identification number registered in Norway
  • with data from 15 April to 15 August 2021.

Exclusion criteria:
  • prior SARS-CoV-2 infection
  • those with an interval between first and second dose of a COVID-19 vaccine that did not adhere to national recommendations (recommended time between doses is 12 weeks with minimum 21 days for Comirnaty/BioNTech-Pfizer and 12 weeks with minimum 28 days for Spikevax/mRNA-1273 Moderna for immunocompetent individuals
  • while for immunocompromised recommended interval is 3 and 4 weeks, respectively).

Follow-up duration (months): 7.70
Vaccines:
  • 1 or 2 doses of either BNT162b2 or mRNA-1273, at least 21 days apart
Variant description :
Variant name: Alpha
Evidence: Direct evidence (effectiveness determined by sequencing cases)
Documents
available

Protocol

NR

Statistical plan

NR

Data-sharing stated: NR
Data accessibility: Correspondence: Elina Seppälä (elina.seppala@fhi.no)
General comment The main concern is the potential for residual confounding. Analysis did not control for ethnicity, SES or symptoms at the time of testing (follow up time was split into unvaccinated and vaccinated and unvaccinated individuals would be unlikely to receive a vaccine if they had symptoms).