"Abstract: ... We conducted a retrospective cohort study of adolescents aged 12–18 with a territory-wide electronic healthcare database of the Hong Kong population... Two age- and sex-matched retrospective cohorts were formed to observe 28 days following the first and second doses of BNT162b2 and estimate the age- and sex-adjusted incidence rate ratios between the vaccinated and unvaccinated... Eventually, the first-dose cohort comprised 274,881 adolescents (50.25% received the first dose) and the second-dose cohort 237,964 (50.29% received the second dose)...
Poisson regression model
... Poisson regression analyses suggested that, for the first-dose cohort, there were no marked differences in the risk of any AESI [adverse events of special interest] upon receiving the vaccine during the observation period of 28 days except for myocarditis (IRR = 9.15, 95% CI 1.14–73.16, P = 0.037). Similarly, the sub-category analyses indicated that the vaccinated group had a five-fold higher incidence rate of 5.34 (95% CI 1.53–18.56) in the cardiovascular system AESIs compared with the unvaccinated group (p = 0.009).
For the second-dose cohort as shown in Table 3, a similar pattern was observed and the IRR for myocarditis was estimated at 29.61 (95% CI 4.04–217.07) and that for cardiovascular system AESIs at 5.92 (95% CI 2.66–13.17)."
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