Figure 2.
Vaccine effectiveness against hospitalisation due to COVID-19, by time since acquiring first booster vaccination status, in 65–79 and ≥ 80-year-olds, in overlapping 8-week-wide observation intervals, based on pooled estimates from Denmark, Navarre (Spain), Portugal and Norway, 1 October 2021‒28 March 2022a
CI: confidence interval; COVID-19: coronavirus disease; VE: vaccine effectiveness.
a The values of VE were obtained by pooling VE estimates from Denmark, Navarre (Spain), Norway and Portugal, using random-effects meta-analysis. The number of events and person-month per period are described in Table 2 and the sample size per period and site can be found in the supplemental material (Supplement S3. Detailed site estimates).
In the graph, each VE figures as a dot, which is overlapped by a vertical line representing the respective 95% CI. For the first two observation intervals (October‒November and November‒December 2021), there were too few data to estimate VE ≥ 12 weeks post-acquiring booster vaccination status in individuals aged ≥ 65 years old. This remained the case for the 65‒79-year-old age group during the third observation interval (December 2021‒January 2022), but not for the ≥ 80-year-old age group.
