Health Desk- 31 July, 2020: Billions of dollars are being invested in the development of vaccines against the coronavirus. Until one arrives, many scientists have turned to tried-and-true vaccines to see whether they may confer broad protection, and may reduce the risk of coronavirus infection, as well.
Old standbys like the Bacille Calmette-Guerin tuberculosis vaccine and the polio vaccine appear to help train the immune system to respond to a broad variety of infections, including from bacteria, viruses and parasites, experts say.
Now a study suggests that people who have received certain routine vaccines in the recent past — including childhood vaccinations like measles-mumps-rubella and polio, as well as adult flu vaccines — have lower coronavirus infection rates than those not recently vaccinated, The New York Times.
But many experts greeted the conclusions with scepticism. The paper, an analysis of electronic health records from the Mayo Clinic, was posted online; it has not been through the peer review process and has not been accepted by a medical journal.
Critics pointed to numerous methodological problems. It is a retrospective study; as such, it points to an association between vaccinations — a marker of overall good health and healthy behaviours — and lower infection risk.
But the study does not prove a cause-and-effect relationship. While scientists generally consider studies like these useful for generating hypotheses that may be worth exploring further, they are far from definitive.
The researchers analysed the immunization records of 137,037 patients who had been tested for infection with the coronavirus, comparing matched pairs of vaccinated and unvaccinated patients who were otherwise similar.
Patients had lower infection rates if they had recently been given the high-dose flu vaccine or had been vaccinated against polio, measles-mumps-rubella, chickenpox, pneumococcal disease, hepatitis A and hepatitis B, or hemophilic influenza Type B, compared with those who had not received those vaccines in recent years.
“The hypothesis we are testing is that the immune system memory is stimulated by the vaccine,” said one of the authors of the paper, Venky Soundararajan, the founder of nference, a company that uses artificial intelligence to synthesize biomedical information.
Dr Christine Stabell Benn, a professor of global health at the University of Southern Denmark who has studied the potential nonspecific effects of vaccines against infectious diseases, said there is “ample evidence” that live attenuated vaccines can increase resistance to seemingly unrelated infections.