I read on https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/janssen.html (mirror):

Fainting After Vaccination

Fainting (syncope) and other events that may be related to anxiety like rapid breathing, low blood pressure, numbness, or tingling can happen after getting any vaccine. Although uncommon, these events are not unexpected, and they are generally not serious.

According to information from the Vaccine Adverse Event Reporting System (VAERS), there were 653 reports of fainting events (fainting and near-fainting) among nearly 8 million doses of J&J/Janssen COVID-19 Vaccine administered in the United States in March and April 2021. This translates to a rate of about 8 fainting events for every 100,000 doses of the J&J/Janssen COVID-19 Vaccine given. These events occurred during the recommended 15-minute wait after vaccination. It’s not clear at this time whether these events were associated with the vaccine or with anxiety, possibly related to preexisting concerns some people who chose to get the one-dose J&J/Janssen COVID-19 Vaccine may have about needles or shots.

By comparison, the rate of fainting after flu vaccination in 2019–2020 was 0.05 per 100,000 doses.

This means that the rate of fainting after a Johnson & Johnson's Janssen COVID-19 Vaccine is 653/(8,000,000/100,000) = 8.16, which is 163 (=8.16/0.05) times higher than the rate of fainting after flu vaccination.

Why is the likelihood of fainting after the Johnson & Johnson's Janssen COVID-19 Vaccine 163 times higher than the likelihood of fainting after flu vaccination?

  • 1
    The info above is from different populations, reporting on different events (fainting and near-fainting vs. fainting), in different types of situations. Comparing apples, oranges and potatoes here.
    – Armand
    Jul 24, 2021 at 4:52
  • 1
    @Armand I'll take 2 kg of apples and 3 kg of potatoes. Jul 24, 2021 at 5:00
  • 3
    And I'll take 100 kg of politically-induced hysteria combined with 10 kg of media-enhanced hysteria to explain the results.
    – Carey Gregory
    Jul 24, 2021 at 5:25
  • 1
    VAERS is not a reliable tool as the data there is not verified. I've asked a related question: medicalsciences.stackexchange.com/questions/29252/… Nov 8, 2021 at 5:17
  • @JonathanReez thanks, let's see if someone can find better sources, perhaps in a country with a better medical system. Nov 8, 2021 at 5:23


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