Need to know: New COVID-19 vaccine data

Colleagues within our HealthPartners Institute – the research and education arm of our organization – have been busy lately, working on various COVID-19 vaccine surveillance projects. These projects have gleaned important insights and validated the safety and efficacy of the vaccines. Below are key takeaways from several high-profile studies.

Safety of COVID-19 mRNA vaccines

An analysis of 6.2 million patients found no serious health effects could be linked to the two mRNA vaccines (Pfizer and Moderna) currently being used to protect against COVID-19. The study was published in the Journal of the American Medical Association (JAMA).

Researchers compared health events within 3 weeks of each patients’ mRNA vaccinations to health events that occurred 3 to 6 weeks after each patients’ mRNA vaccinations. They looked at 23 potential side effects that were monitored during the vaccine clinical trials and reported among those who received the vaccines after authorization.

After identifying potential side effects and conducting complex statistical analyses, the researchers concluded that neither mRNA vaccine currently in-use produced any “safety signals,” or events occurring at increased rates as compared to the control or comparison period.

Notably, the study identified 34 cases of heart inflammation, like myocarditis and pericarditis, in patients aged 12 to 39 years. 85% of these cases occurred in males. 82% of these people were hospitalized for a median of 1 day. The authors calculated that among patients aged 12 to 39 years, there is a slight risk of 6.3 additional myocarditis cases per million COVID-19 vaccine doses during the first week after vaccination. Other data show that heart inflammation events are far more likely after COVID-19 infection than vaccination.

Read the full study.

Pregnancy and miscarriage

Also in JAMA, new data show that mRNA vaccines (Pfizer and Moderna) administered during pregnancy did not increase the risk of miscarriage.

HealthPartners Institute led this study, which compared the odds of having received a COVID-19 vaccine in the 28 days prior to miscarriage to the odds of having received a COVID-19 vaccine in the 28 days prior to pregnancy that did not end in miscarriage across similar gestational ages.

Researchers found that after adjusting for maternal age and other important risk factors, the proportion of miscarriages to ongoing pregnancies among those who were vaccinated was nearly identical to the proportion of miscarriages to ongoing pregnancies among those who were unvaccinated (an odds ratio of 1.02).

In this large population of pregnancies from 8 health systems COVID-19 vaccines had no impact on miscarriages.

Read the full study.

Effectiveness of COVID-19 vaccines

Recent data in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report shows the effectiveness of COVID-19 vaccines against COVID-19 hospitalizations and emergency and urgent care encounters during June and July remained similar to the vaccine effectiveness prior to Delta variant predominance.

Read the full study.

And, in the New England Journal of Medicine (NEJM), researchers analyzed more than 41,000 hospitalizations and more than 21,000 emergency and urgent care visits during January to June 2021. This is when the Alpha variant was still the dominant strain of COVID-19 in the United States. They found strong effectiveness across the board:

  • Full 2-dose mRNA vaccination was 91% effective at preventing emergency department and urgent care encounters, 89% effective at preventing hospitalizations, and 90 percent effective at preventing ICU admissions. Rates were similar for both the Pfizer-BioNTech and Moderna vaccines.
  • The Janssen (Johnson & Johnson) vaccine was 73% effective at preventing emergency department and urgent care encounters and 68% effective at preventing hospitalizations.

Read the full study.

Additional resources

Our institute colleagues will continue to evaluate ongoing COVID vaccine efficacy and safety, and we’ll share more when it becomes available. In the meantime, more information about COVID-19 safety and efficacy is also available on myPartner.

Colleagues are also invited to attend our upcoming colleague vaccine forums, These are 30-minute virtual sessions led by our clinicians and focused on helping answer common questions about vaccines. View the schedule or see past recordings.

David Martinson

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