BACKGROUND: Rare cases of thrombosis and thrombocytopenia (Thrombosis with Thrombocytopenia Syndrome or TTS) have been associated with two COVID-19 adenovirus vector vaccines: the CHAdOx1 nCoV-19 Vaxzevria (Oxford/AstraZeneca vaccine) and the JNJ-7836735 Johnson and Johnson vaccine (Janssen vaccine). It is unknown if TTS is a class-mediated effect of adenovirus-based vaccines or if it could worsen known hypercoagulable states. Since most cases of TTS happen in women of childbearing age, pregnancy is a crucial risk factor to assess. Understanding these risks is important for advising vaccine recipients and future adenovirus-vector vaccine development. METHODS: To explore the potential associations of adenovirus-based vaccine components with symptoms of TTS in the general clinical trial population and in pregnant women in clinical trials, we conducted a systematic review and meta-analysis of adenovirus-based vector vaccines to document cases of thrombocytopenia, coagulopathy and or pregnancy from January 1 st, 1966, to August 9 th, 2021. RESULTS: We found 167 articles from 159 trials studies of adenovirus- vector based vaccines, 123 of which targeted infectious diseases. In the general population, 20 studies reported an event of thrombocytopenia and 20 studies indicated some coagulopathy. Among pregnant women, of the 28 studies that reported a total of 1,731 pregnant women, thrombocytopenia or coagulopathy were not reported. CONCLUSION: In this systematic review and meta-analysis there was no class-wide effect of adenovirus vector vaccines towards thrombocytopenia or coagulopathy events in the general population or in pregnant women.

  • Pregnant women
  • Vaccine/vaccination
  • Safety
  • COVID-19