Heterologous Adaptive Immunity Due to MMR and Tdap Vaccine

Researchers from the USA have shown that prior Measles-Mumps-Rubella (MMR) or Tetanus-Diphtheria-pertussis (Tdap) vaccination could reduce the risk of severe outcomes in COVID-19. Researchers provided evidence that SARS-CoV-2 reactivated memory  T-cells previously generated by MMR and Tdap vaccination. This is called heterologous adaptive immunity. The study results are published on a pre-print server.  The antigen-specific T-cell assay was used to determine whether SARS-CoV-2 specific T cells from convalescent individuals or recipients of COVID-19 vaccines cross-reacted with antigens present in MMR and Tdap vaccines.

The researchers identified a strong correlation between responses to the SARS-CoV-2 spike and nucleocapsid proteins and responses to MMR and Tdap vaccine proteins in both convalescent individuals and those who had been immunized with COVID-19 vaccines. A propensity-weighted analysis of 73,582 COVID-19 patients adjusted for multiple patient characteristics was selected to determine whether disease severity was attenuated in individuals with prior MMR or Tdap vaccination.

This revealed that severe outcomes (hospitalization, transfer to intensive care, or death) were reduced in MMR- and Tdap- vaccinated individuals by 38-32% and 23-20%, respectively. The researchers concluded that intentional MMR or Tdap vaccine-induced heterologous immunity to SARS-CoV-2 could enhance the effectiveness of SARS-CoV-2 vaccines.

Ref link: https://www.biorxiv.org/content/10.1101/2021.05.03.441323v1