Protection of COVID-19 from influenza vaccination?Experts are wary of new research

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Toronto, OntarioCTV network) — Experts, despite recent research results, do not have enough evidence to support the hypothesis that influenza-vaccinated individuals may be more resistant to COVID-19. Is called.

The study, published in the American Journal of Infection Control, was conducted by researchers at the University of Michigan, examining data from 27,201 residents of Michigan who had undergone COVID-19 testing by July 15, 2020. .. I was previously vaccinated against the flu.

According to the findings, the probability of a positive COVID-19 test was reduced by 24% in patients vaccinated against the flu vaccine compared to patients who were not vaccinated against the flu.

In addition, the study found that flu-vaccinated residents were less likely to require hospitalization or mechanical ventilation and had shorter hospital stays.

But importantly, researchers found that there was no difference in mortality or the need for intensive care between those who were vaccinated against the flu and those who were not.

The authors of the study acknowledged that their study could not determine why influenza-vaccinated individuals appeared to be better against COVID-19 than other subjects, but they were “hypothetical.” Is plausible. “

Researchers have hypothesized that influenza vaccines may also provide a protective effect against new coronaviruses due to a process called “trained immunity.”

Rob Kozak, a clinical microbiologist at Sunnybrook Hospital in Toronto who helped isolate the SARS-CoV-2 virus in March 2020 and was not involved in the study, has two immune systems: the innate immune system and the innate immune system. I explained that there are two branches. Adaptive immune system.

The innate immune system is the “first line of defense” and has no memory of a particular pathogen, so it only attacks those that invade the body.

The adaptive immune system, on the other hand, can be trained to recognize specific pathogens.

“The idea of ​​trained immunity is that stimulatory molecules from any pathogen can get it. [innate] The immune system really ignited and activated, “Kozak said. CTVNews.ca During a telephone interview on Thursday.

According to researchers, this is sufficient for the introduction of influenza pathogens during vaccination to activate the innate immune system, potentially infecting SARS-CoV-2, the virus that causes COVID-19. It means to repel.

Kozak called it an “interesting hypothesis,” but he said there was no data in this particular study to draw such conclusions.

Socio-economic situation
Dr. Michael Silverman, Head of Infectious Diseases at the London Health Science Center and St. Joseph Healthcare London, London, Ontario. Those who were not involved in the study stated that researchers could only show relevance, not causality.

He said that the reduced COVID-19 infection rate and serious outcomes of influenza vaccinated individuals may be due to socioeconomic factors rather than immunological factors such as trained immunity. Said that was high.

“People who get the flu vaccine tend to take care of their health and see a doctor,” he explained in a telephone interview Thursday.

“Because this is an American study, vaccinations tend to be insured, but people with limited insurance or limited visits can only get the flu shot. I’m not going … “

Kozak agrees that people vaccinated against the flu are more likely to take care of their health in accordance with public health guidelines. If they have access to vaccines, they are likely to have insurance plans and jobs that allow them to work remotely, as opposed to those who work in low-paying jobs that may be exposed to the virus. He says.

“We hope that this data will be repeated in other populations, including those outside the United States, so that we can explain differences in habits and lifestyles, and all those types of socio-economic factors. “He said.

For their benefit, researchers pointed out at the limits of the study that they were unable to control the different socio-economic factors between the influenza vaccination group and other groups, and further research. Is needed.

“Prospective studies that explain these differences are needed to investigate the possible protective effects of influenza vaccines on the susceptibility and outcome of COVID-19,” the study said.

Insufficient influenza vaccination
Kozak said the researchers’ hypothesis that influenza vaccines are potentially defensive against COVID-19 is worth further investigation, but emphasized the importance of obtaining the COVID-19 vaccine. did.

“I don’t want anyone to be deprived of the fact that I shouldn’t be vaccinated with the COVID vaccine,” he said. “They absolutely need to get the COVID vaccine … Influenza vaccination does not protect you from anything but influenza.”

Silberman added that the flu season is over and it’s not time to attack healthcare providers with a request for people to be vaccinated against the flu.

“All family doctors’ clinics and pharmacies are ready to start vaccination with the COVID vaccine, so we need to throw more people at them to get the flu shot based on related studies. Do you have one? No, I don’t think so, “he said.

But in the fall, Silberman advised people to be vaccinated against the flu as they did in other years. Hopefully, by that time, everyone who wants to be vaccinated against COVID-19 has already been vaccinated against the flu.

“I think this is an interesting study, but it won’t change our behavior. If it was announced in September before the COVID vaccine became available, it would be people in October and November. Will be another argument that people should be vaccinated against the flu, “he said. “Further research is needed.”

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Nicole [email protected] (416) 384-5000