mRNA (BNT162b2) COVID-19 vaccination increased risk of Bell’s palsy: a nested case control and self-controlled case series study

BACKGROUND: Observable symptoms of Bell’s palsy following vaccinations may arouse concern over the safety profiles of novel COVID-19 vaccines in the general public. However, there are only a few studies on Bell’s palsy following mRNA COVID-19 vaccination with inconclusive findings. This study aimed to update the previous analysis on the risk of Bell’s palsy following mRNA (BNT162b2) COVID-19 vaccination. METHODS: This study included cases aged ≥16-years-old with a new diagnosis of Bell’s palsy within 28 days after BNT162b2 vaccinations from the population-based electronic health records in Hong Kong, using a nested case-control and self-controlled case series (SCCS) analyses were employed. The association between Bell’s palsy and BNT162b2 was evaluated using conditional logistic and Poisson regression in nested case-control and SCCS analysis, respectively. RESULTS: A total of 54 individuals were newly diagnosed with Bell’s palsy after BNT162b2 vaccinations. The incidence of Bell’s palsy was 1.58 (95% CI:1.19-2.07) per 100,000 doses administered. The nested case-control analysis showed significant association between BNT162b2 vaccinations and Bell’s palsy (Adjusted OR: 1.543, 95%CI:1.123 - 2.121), with up to 1.112 excess events per 100,000 people receiving two doses of BNT162b2. An increased risk of Bell’s palsy was observed during the first 14 days after the second dose of BNT162b2 in both nested case-control (Adjusted OR: 2.325, 95%CI:1.414 – 3.821) and SCCS analysis (Adjusted IRR=2.44, 95%CI:1.32-4.50). CONCLUSION: There is an overall increased risk of Bell’s palsy following BNT162b2 vaccination, particularly within the first 14 days after the second dose, but the absolute risk was very low

Thromboembolic events and hemorrhagic stroke after mRNA (BNT162b2) and inactivated (CoronaVac) covid-19 vaccination : a self-controlled case series study

Background: This study aims to evaluate the association between thromboembolic events and hemorrhagic stroke following BNT162b2 and CoronaVac vaccination. Methods: Patients with incident thromboembolic events or hemorrhagic stroke within 28 days of covid-19 vaccination or SARS-CoV-2 positive test during 23 February to 30 September 2021 were included. The incidence per 100,000 covid-19 vaccine doses administered and SARS-CoV-2 test positive cases were estimated. A modified self-controlled case series (SCCS) analysis using the data from the Hong Kong territory-wide electronic health and vaccination records. Seasonal effect was adjusted by month. Findings: A total of 5,526,547 doses of BNT162b2 and 3,146,741 doses of CoronaVac were administered. A total of 334 and 402 thromboembolic events, and 57 and 49 hemorrhagic stroke cases occurred within 28 days after BNT162b2 and CoronaVac vaccination, respectively. The crude incidence of thromboembolic events and hemorrhagic stroke per 100,000 doses administered for both covid-19 vaccines were smaller than that per 100,000 SARS-CoV-2 test positive cases. The modified SCCS detected an increased risk of hemorrhagic stroke in BNT162b2 14-27 days after first dose with adjusted IRR of 2.53 (95% CI 1.48-4.34), and 0-13 days after second dose with adjusted IRR 2.69 (95% CI 1.54-4.69). No statistically significant risk was observed for thromboembolic events for both vaccines. Interpretation: We detected a possible safety signal for hemorrhagic stroke following BNT162b2 vaccination. The incidence of thromboembolic event or hemorrhagic stroke following vaccination is lower than that among SARS-CoV-2 test positive cases; therefore, vaccination against covid-19 remains an important public health intervention. Funding: This study was funded by a research grant from the Food and Health Bureau, The Government of the Hong Kong Special Administrative Region (reference COVID19F01)