Study finds no link between Pfizer and Moderna vaccine and selected serious health outcomes

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  • A study looked at possible adverse events after vaccination.
  • The researchers focused on the two mRNA vaccines, Pfizer and Moderna.
  • They monitored more than six million people after receiving one and both doses of the mRNA vaccines.

A new study found no significant link between vaccination with mRNA Covid-19 vaccines and selected serious health outcomes one to 21 days after vaccination.

The study published in JAMA Network monitored the possibility of negative post-vaccine outcomes for people who got either the Pfizer or Moderna mRNA vaccines.


The researchers monitored almost 12 million total doses of mRNA vaccines administered to 6.2 million people from 14 December 2020 through 26 June 2021.

The study authors looked at 23 possible adverse events that may take place after vaccination based on previous vaccine trials results. This included blood clots, stroke, pulmonary embolism, Bell's palsy and narcolepsy.

The researchers also used patient medical records as part of the surveillance to investigate potential emerging concerns.

Low risk of adverse events

The study results show that the incidence of selected serious outcomes from mRNA Covid-19 vaccines was not significantly higher from one to 21 days post-vaccination compared to 22 to 42 days post-vaccination.

The study results show that during days 0 to 21 post-vaccination surveillance, there were a total of 34 cases of myocarditis/pericarditis, and nearly all had recovered at record review. The cases were largely found within 0 to five days after vaccination.

The researchers found that during the 21 days after vaccination, 12 people received a diagnosis of acute respiratory distress syndrome, six people of multisystem inflammatory syndrome, and 29 of narcolepsy.

The researchers also note that there is no evidence of blood clotting outcomes associated with mRNA vaccines.

The authors of the study added that they will continue to monitor vaccination outcomes.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

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