Listen for Concerns About Blood Clots With COVID-19 Vaccines

Patients will ask whether COVID-19 vaccines cause blood clots.

This is due to reports of serious blood clots along with low platelets after the Johnson & Johnson/Janssen vaccine in the U.S...and the AstraZeneca vaccine in other countries. Both are viral vector vaccines.

The risk is extremely RARE...with just a handful of cases to date in about 8 million doses of the Janssen vaccine given in the U.S.

Now the Janssen vaccine emergency use authorization (EUA) fact sheets will warn about this issue.

Continue to urge patients to get ANY COVID-19 vaccine ASAP...and send patients who are worried about blood clots to your pharmacist. Your pharmacist can help put the situation in perspective.

For example, the clot risk due to severe COVID-19 infection is MUCH higher than the risk with the Janssen vaccine.

Plus there are NO reports of this issue with the Pfizer-BioNTech or Moderna mRNA vaccines...after over 200 million doses.

Be aware, most clots with the Janssen or AstraZeneca vaccines are unusual...such as in the brain or abdomen.

And most reports with the Janssen vaccine are in females under age 50...about 1 to 2 weeks after vaccination.

Expect your pharmacist to reassure patients that there's little concern about clotting if the vaccine was given over 3 weeks ago.

But stay alert for patients complaining of severe headache or abdominal pain, blurred vision, or shortness of breath...especially within 3 weeks of the Janssen vaccine. These patients need prompt medical care.

Also listen for vaccine patients asking about taking aspirin or another blood thinner "just in case." There's no evidence this helps...and it may increase bleeding risk.

Help report serious adverse events and administration errors to the Vaccine Adverse Event Reporting System (VAERS). Safety systems for vaccines are working as they catch potential issues.

See our COVID-19 Vaccination FAQs for more details about safety and efficacy...and answers to other common questions.

Key References

  • (4-26-21)
  • (4-26-21)
  • N Engl J Med Published online Apr 9, 2021; doi:10.1056/NEJMoa2104840
  • N Engl J Med Published online Apr 9, 2021; doi:10.1056/NEJMoa2104882
  • N Engl J Med Published online Apr 16, 2021; doi:10.1056/NEJMoa2105385
  • N Engl J Med Published online Apr 16, 2021; doi:10.1056/NEJMoa2106315
Pharmacy Technician's Letter. May 2021, No. 370501

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