Published in the National Library of Medicine, National Center for Biotechnology Information, with the contribution of the following, Alice Wynne; Thomas Bale; Rebecca Edwards; Natalie Wright and Petra Manley After 2 years of no community outbreaks of COVID-19, the Falkland Islands (FI) reported their first community case in April 2022. Because of high vaccine coverage (88% of entire population), no specific control measures were instigated, and cases spread rapidly. We undertook a retrospective cohort study to determine the extent of transmission and the effectiveness of COVID-19 vaccine in a population with limited natural immunity.
We extracted data on age, sex, and vulnerability for the FI registered population from a patient information system and linked to COVID-19 case line-list and vaccination datasets. Cases were individuals with positive SARS-CoV-2 PCRs or Lateral Flow Devices (LFDs), from 26 April to 30 June 2022. Univariable analyses compared case risk factors to non-cases.
Relative vaccine effectiveness was calculated using Poisson regression with robust error variance, comparing against individuals with vaccination more than the 20 weeks prior to the outbreak. Models were adjusted for age, sex, extreme vulnerability, and previous infection. Of the 3,343 registered population, 44% (n = 1,467) were cases, with no COVID-19 hospitalizations or deaths.
In univariable analysis, being female (RR 1.12, p = 0.004) and under 18 years (RR 1.
70, p<0.001) were associated wit.