Coadministration of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine with BNT162b2 mRNA vaccine (Pfizer-BioNTech) may result in delayed immunogenicity to the COVID-19 vaccine, according to a recent report published in the American Journal of Case Reports.

The case involved a 29-year-old female who was administered the Tdap vaccine (in the right arm) 1 day after receiving the first dose of the BNT162b2 vaccine (in the left arm). At the time of administration, the Centers for Disease Control and Prevention (CDC) had recommended that the COVID-19 vaccine be administered 14 days before or after any other vaccines.

To allay the patient’s concerns over potential efficacy issues, serological testing was conducted to assess for immunity. Testing revealed a delay in the development of SARS-CoV-2 spike protein antibodies, with no detectable immune response 6 weeks after vaccination. Subsequent testing 8 weeks after the second dose revealed positive anti-spike antibody levels. Tdap vaccine immunogenicity was not affected by coadministration.

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“Although the administration of Tdap with COVID-19 vaccine in our case caused delay in immunogenicity, it did not negate the ability of the BNT162B2 mRNA vaccine to elicit an adequate immune response,” the study authors noted. “The reason for delay in immune response with coadministration of COVID-19 vaccines with other vaccines is unknown and further studies are needed.”

According to current CDC guidelines, COVID-19 vaccines and other vaccines may now be administered without regard to timing. If multiple vaccines are given at a single visit, different injection sites should be used.


Chilimuri S, Mantri N, Shrestha E, Sun H, Gongati S, Zahid M, Kelly P. BNT162b2 mRNA vaccine interference with co-administration of Tdap vaccine. American Journal of Case Reports. Published online July 11, 2021. doi 10.12659/AJCR.933003

This article originally appeared on MPR