Once the doors start to open again and people venture out without taking the precautions of Covid-19 for a year, it is possible for new strains of flu to circulate that scientists did not predict, said Cody Meissner, an infectious disease specialist. and a pediatrician at Tufts Children’s Hospital, who also serves on the FDA vaccine advisory panel. Without a strong enough vaccine, the country fatigued by the pandemic could have a severe flu season as soon as it emerges from the fight against the coronavirus.
“We can have a combination of low public health measures at the population level with a low-effectiveness vaccine. And then you can have a violent flu season next year, ”said Lawrence Gostin, professor of global health law at Georgetown University.
Concerns about the indirect effects of the shockingly quiet flu season surfaced earlier this month at a meeting of the Food and Drug Administration’s independent vaccine advisory committee. While experts have suggested that there are lessons to be learned from last year’s flu season that can help prevent high flu rates in future years, they also had a hard time designing what the coming winter might bring.
“What we asked them during that meeting was, ‘Was there ever a time like this?’ Where there was very little flu circulating, you can make a judgment call about what happened next year, but that really is unprecedented, ”said Paul Offit, a vaccine expert at the University of Pennsylvania and a member of the FDA’s vaccine board. .
The flu is already a difficult virus to track, Gostin said, because it mutates more quickly than other familiar viruses, such as measles. The act of rapidly changing the flu creates several strains each year.
The process of predicting which strains of influenza will dominate each flu season is a global effort. The World Health Organization brings together experts twice a year to predict flu strains – once for each of the northern and southern hemispheres – based on data collected by laboratories around the world. They include the Centers for Disease Control and Prevention, one of WHO’s six “collaborating centers” for influenza research.
At the Northern Hemisphere meeting in February, experts analyze which strains are circulating in the Southern Hemisphere as autumn approaches – and use that information to interpret which strains may reach the northern part of the globe months later. In the United States, the FDA vaccine advisory committee reviews these recommendations and makes a final decision on the composition of the flu vaccines that the agency will license.
Kawsar Talaat, an assistant scientist at Johns Hopkins with experience in infectious diseases, said that experts watch how the virus evolves throughout the season and which strains are dominant at the end of the season.
There are few precedents for the most recent flu season in the United States. The 2011-12 flu season set records for the lowest and shortest flu peak, according to the CDC. Last season’s figures are still only a third of the 2011-12 season rate, reports the agency.
The low previous year did not appear to lead to a particularly bad flu season in 2012-13, Talaat said, adding that the vaccine’s effectiveness that year was in line or better than most years. She said it is too early to know what the flu season will be like next fall or to predict the likely effectiveness of the flu vaccine.
“In 2011-2012, we had almost no flu season and this happens from year to year. And then, last year, we had a flu season with three phases and three peaks, which was also very unusual. So flu biology is a fascinating topic, ”said Talaat.
Offit said that the low levels of the virus this season still generate enough circulation for the FDA advisory committee to choose strains for a vaccine and that he is not concerned about the vaccine for next fall.
“The belief is that there were enough viruses circulating to be able to choose what would likely be the strains associated with next year’s flu outbreak,” said Offit.
The flu was not the only winter respiratory virus to see low numbers this season. Rates of respiratory syncytial virus have also dropped, said Offit. The disappearance of winter respiratory viruses is causing health experts to wonder if Covid-19’s mitigation strategies could become a necessary tool to combat them every year.
“I mean, could we reasonably, in a winter month, wear masks at least when we are outdoors in large crowds?” Offit said. “Did we learn that or are we willing to learn, or are we comfortable with hundreds of thousands of cases of hospitalizations for influenza and 10 out of 1000 deaths? I suspect the answer is B. We are comfortable with it, we are willing to have it, even though we have just learned, there is a way to avoid it. “
People are ready for life to return to normal, Gostin said, and the fatigue of the Covid-19 pandemic can cause people to abandon masking and social detachment at the right time for the flu.
“Remember that, after the 1918 flu pandemic, most people didn’t realize what happened when it ended. But what happened was the noisy decade of the 20s, ”said Gostin. “People started to get together, to mix, to hug, to kiss. All the things that they lost. They filled the theaters and stadiums and went back to the church. It is likely to happen this fall and it makes the flu virus very happy. “