Pre-existing memory T cells generated by prior MMR or Tdap vaccination and activated by SARS-CoV-2 infection give the immune system a head start in responding, thereby lowering the risk of severe covid-19
NEW DELHI: The Measles-Mumps-Rubella (MMR) vaccine, given during early childhood, and Tetanus-Diphtheria-Pertussis (Tdap) vaccine, given every 10 years, may have an unexpected bonus - preventing severe covid-19, scientists from Harvard Medical School have found.
The research findings come at a time when India is bracing for a third wave of coronavirus infections that may have much bigger impact children this time around. Researchers indicated that it was possible that these vaccines elicit cross-reactive memory T cells capable of responding to protein targets called antigens that are present in other microbes which cause diseases, including the viral antigens in SARS-CoV-2.
Pre-existing memory T cells generated by prior MMR or Tdap vaccination and activated by SARS-CoV-2 infection give the immune system a head start in responding, thereby lowering the risk of severe covid-19, scientists said in their study which has been also published in peer reviewed journal Med.
To investigate whether MMR and Tdap vaccines provide additional protection against covid-19, researchers at Brigham and Women’s Hospital under Harvard Medical School conducted laboratory-based analyses using sensitive, new techniques to detect and characterize T cell responses to antigens.
“Our Cleveland Clinic colleagues observed an association where individuals with covid-19 who had either MMR or Tdap vaccines had a much lower frequency of going to the intensive care unit or dying," said co-author Andrew Lichtman, an immunologist and senior investigator in the Brigham’s Department of Pathology and professor of Pathology at Harvard Medical School.
"Although previous smaller studies suggested a similar link, our in-depth epidemiological analyses, together with our basic research results, suggest that these commonly given vaccines may protect against severe disease," Lichtman said.
"During the covid-19 pandemic, we know that there was a marked decline in routine vaccinations for children and adolescents," said corresponding author Tanya Mayadas, PhD, a senior scientist in the Brigham’s Department of Pathology and professor of Pathology at Harvard Medical School. “Our findings emphasize the importance of routine vaccination for children and adults. We know vaccines protect against devastating diseases, and we’re now seeing growing evidence that some of them provide a degree of protection against severe covid-19 disease."
The authors note that while their laboratory-based findings are strengthened by the epidemiological observations, more work is needed to assess the association between the MMR and Tdap vaccinations and severity of covid-19 disease to determine if the relationship is a causal one. Prospective studies of vaccination and patient outcomes may help distinguish correlation from causation.
"With regards to covid-19 vaccines, our findings predict that although MMR and Tdap are not a substitute for covid-19 vaccines they may afford greater and more durable protection, possibly against emerging spike variants than the covid-19 vaccine alone," said Mayadas. “And in areas where the covid-19 vaccines are not available, they could protect infected individuals from developing severe disease."
The Harvard study is similar to a research conducted by BJ Medical College in Pune, India, which showed that measles vaccine had an efficacy rate of 87.5% against the SARS-CoV-2 virus. The study, published in the peer-reviewed journal Human Vaccines and Immunotherapeutics, also indicated that measles vaccine might offer long-term protection against covid infection in children.
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