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8 Week mRNA COVID-19 Vaccine (Pfizer or Moderna) Interval Consideration

Last updated: May 2, 2022

Recently, the Centers for Disease Control and Prevention (CDC) updated its COVID-19 vaccination guidance in an effort to further decrease the very small risk of myocarditis and pericarditis in some people. Myocarditis is inflammation of the heart muscle and pericarditis
is inflammation of the lining outside the heart. In both cases, the body’s immune system is causing inflammation in response to an infection or other trigger. Most symptoms resolve within one to two days with conservative treatment. The risk of myocarditis/pericarditis among males 18 through 39 is low. According to the Vaccine Safety Datalink (VSD), it is lower with Pfizer than Moderna. Data show that myocarditis from primary COVID-19 infection occurs at a rate as high as 450 per million in young males. Young males infected with the virus are up to six times more likely to develop myocarditis as those who have received a mRNA COVID-19 vaccine.

To further reduce the risk of myocarditis or pericarditis, a longer interval between the first and second dose of mRNA vaccine (Pfizer or Moderna) of 8 weeks may be appropriate for some people ages 12 and older, especially for males ages 12 through 39.

Data also show that the risk of myocarditis may be higher for Moderna than Pfizer.  Therefore, it is recommended that individuals who are eligible for the Pfizer COVID-19 vaccine choose this vaccine for their primary series and booster.

Considerations for Extending Second Dose mRNA Vaccine (Pfizer or Moderna) Time Interval to 8 weeks:

  • Benefits people ages 12 through 64 who are not moderately or severely immunocompromised.
  • Stronger immune response. Data show that a longer interval between first and second doses may give the body a chance to build a stronger immune response, increasing the effectiveness of these vaccines.
  • Would help lower the (small) risk of myocarditis and pericarditis, which has been associated—mostly among adolescent and young adult males ages 12 through 39.

These additional considerations followed a thorough evaluation of the latest safety and effectiveness data, and evidence from hundreds of millions of COVID-19 vaccines that have already been safely administered in the United States, and the billions of vaccines administered in other countries. Specific data can be found on the CDC website.

Regardless of the interval between the first and second dose, mRNA vaccines are highly effective at reducing the risk of hospitalizations and serious complications from COVID-19 infection. People who have already received their primary mRNA series at the 3-week or 4- week interval remain well protected, specifically if they have received a booster dose.

If you have questions specific to your situation, speak with your medical provider.

To schedule an appointment for a COVID-19 vaccine, please visit www.aacounty/covidvax.


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