‘A perfect storm’
“Now you kind of have the perfect storm,” Dr. Chin-Hong said. “It’s not a good situation for COVID with the variants that are emerging. For influenza, not having seen a lot of influenza the last 2 years, we’re probably more susceptible to getting infected.”
RSV cases rose during summer 2021, but now the weather is colder, and people are interacting more closely. “And it’s very, very transmissible,” he said.
Dr. Chin-Hong also predicted that “even though we don’t have a lot of COVID now, COVID will probably pick up.”
The rise in RSV was unexpected by some experts. “This early influenza is also a bit of a surprise and may be influenced by the fact that lots of us are going back and seeing each other again close-to-close, face-to-face in many enclosed environments,” Dr. Schaffner said.
He estimated the 2022-2023 flu season started 4-6 weeks early “and it’s taken off like a rocket. It started in the Southeast, quickly went to the Southwest and up the East Coast. Now it’s moving dramatically through the Midwest and will continue. It’s quite sure to hit the West Coast if it isn’t there already.”
A phenomenon by any other name
Some are calling the situation an “immunity debt,” while others dub it an “immunity pause” or an “immunity deficit.” Many physicians and immunologists have taken to social media to push back on the term “immunity debt,” saying it’s a mischaracterization that is being used to vilify COVID precautions, such as masking, social distancing, and other protective measures taken during the pandemic.
“I prefer the term ‘immunity gap’ ... which is more established in the epidemiology literature, especially given the politicization of the term ‘immunity debt’ by folks recently,” Dr. Messacar said.
“To me, the immunity gap is a scientific observation, not a political argument,” he added.
In a July 2022 publication in The Lancet, Dr. Messacar and his colleagues stated that “decreased exposure to endemic viruses created an immunity gap – a group of susceptible individuals who avoided infection and therefore lack pathogen-specific immunity to protect against future infection. Decreases in childhood vaccinations with pandemic disruptions to health care delivery contribute to this immunity gap for vaccine-preventable diseases, such as influenza,measles, and polio.”
The researchers noted that because of isolation during the pandemic, older children and newborns are being exposed to RSV for the first time. Returning to birthday parties, playing with friends, and going to school without masks means “children are being exposed to RSV, and that’s likely the reason that RSV is moving early and very, very substantially through this now expanded pool of susceptible children,” Dr. Schaffner said.
How likely are coinfections?
With peaks in RSV, flu, and COVID-19 cases each predicted in the coming months, how likely is it that someone could get sick with more than one infection at the same time?
Early in the pandemic, coinfection with COVID and the flu was reported in people at some centers on the West Coast, Dr. Auwaerter said. Now, however, “the unpredictable nature of the Omicron subvariants and the potential for further change, along with the never-before-seen significant lessening of influenza over 2 years, leave little for predictability.
“I do think it is less likely, given the extent of immunity now to SARS-CoV-2 in the population,” Dr. Auwaerter said.
“I most worry about viral coinfections ... in people with suppressed immune systems if we have high community rates of the SARS-CoV-2 and influenza circulating this fall and winter,” he added.
Studies during the pandemic suggest that coinfection with the SARS-CoV-2 virus and another respiratory virus were either rare or nonexistent.
Dr. Schaffner said these findings align with his experience at Vanderbilt University, which is part of a CDC-sponsored network that tracks laboratory-confirmed RSV, flu, and COVID cases among people in the hospital. “Coinfections are, at least to date, very unusual.”
There needs to be an asterisk next to that, Dr. Schaffner added. “Looking back over the last 2 years, we’ve had very little influenza, and we’ve had curtailed RSV seasons. So there hasn’t been a whole lot of opportunity for dual infections to occur.
“So this year may be more revelatory as we go forward,” he said.