The effectiveness of the Pfizer and AstraZeneca COVID-19 vaccines turns negative against severe COVID-19 months after administration, according to a new study.
A single dose of the Pfizer vaccine was pegged at negative 121 percent effectiveness on day 84 and negative 85 at day 98. A second Pfizer dose held up better, but still dipped below 50 percent at day 98, researchers concluded.
A single dose of the AstraZeneca vaccine turned negative at day 70 and a second dose turned negative at day 84, according to the paper, which was published in the International Journal of Epidemiology.
Negative effectiveness means a vaccinated person is more likely to experience a condition than an unvaccinated person….