The Return of Flu: Signs Point to Possible Severe Season
Risk of co-infection with SARS-CoV-2 could increase
A possible severe influenza season is on the horizon, in part because COVID-19 shutdowns and precautions led to a historically low flu season in 2019-2020, said Rochelle Walensky, MD, director of the Centers for Disease Control and Prevention (CDC).
“We had so little disease last year, population immunity will be lower, putting us all at increased risk for influenza this year, especially among those most vulnerable,” she explained at an Oct. 12, 2021, flu press conference held by the National Foundation for Infectious Diseases.
“When there is active flu one year to another, then we have more people — not just who are vaccinated — but people who were actually sick and have built up some protective immunity,” Walensky said. “That immunity actually helps us, especially those who have not been vaccinated. If they had the flu last year, they may have had some residual immunity against getting the flu this year.”
Another signal of more circulating flu virus in the 2021-2022 season is the early, unseasonal appearance of respiratory syncytial virus (RSV).
“We have had a large amount of RSV in the last couple of months, which is atypical for this seasonal virus,” she said. “We did not see some of these respiratory viruses last year because we were taking those prevention and mitigation strategies [for COVID-19].”
CDC surveillance conducted at Vanderbilt University in Nashville confirms this unusual emergence of RSV, said William Schaffner, MD, professor of preventive medicine at the school and medical director of the National Foundation for Infectious Diseases (NFID).
“We have seen an unseasonal increase with RSV, and that’s continuing,” he said. “Is that a harbinger of a worse influenza season? We don’t know, but we certainly don’t want a ‘twindemic’ of both COVID and influenza. Let’s get vaccinated against both.”
Flu vaccination has faced historical resistance from people who fear or simply refuse the shot, much as has been seen currently with the COVID-19 pandemic. The shots for flu and SARS-CoV-2 can be given at the same time.
“We can give flu vaccine and COVID vaccine on the same visit,” said Patsy Stinchfield, RN, MS, CPNP, president-elect at the NFID. “You don’t need to separate them, but usually we will administer them in separate arms.”
In a recent NFID survey, 44% of U.S. adults said they are unsure or do not plan to get vaccinated against influenza during the 2021-2022 flu season.1 Another troubling finding was that 23% of people at high risk of flu complications said they were not planning to get vaccinated. People at higher risk of flu complications include pregnant women, children 5 years of age and younger, those 65 years of age and older, and those with chronic conditions, such as diabetes, lung conditions or heart disease. The CDC recommends everyone 6 months of age and older be vaccinated for influenza.
Those survey findings caused alarm, but “the pandemic does seem to be driving changes in some prevention behaviors,” Schaffner said. “For example, 54% of U.S. adults plan to wear a mask during flu season. And 45% say the pandemic will make them more likely to stay home from work or school if they are sick. That’s good news.”
Vaccine Myths Resurface
Cited reasons in the survey for not getting vaccinated included the age-old “I never get the flu” and the vaccine is not effective. Another long-imploded myth came up after an unidentified reporter asked: “How do we really know the flu vaccine does not cause flu?”
“You cannot get flu from the flu vaccine. That’s an old myth — please, you can’t do that,” an exasperated Schaffner said. “Virtually all the vaccines are made up of only parts of the virus so there is no way that they can recreate the virus in your body to give you influenza. [No one] can hide behind that as a reason not to get vaccinated. As we say in Tennessee, ‘That dog won’t hunt.’”
Since the discussion had been breached by serious misinformation, Schaffner took the trouble to explain why the live, attenuated nasal spray vaccine cannot give anyone flu either.
“It is miracle of modern science that the virus can stimulate your immune system, but it cannot get down into your chest,” he said. “It can’t multiply there. It’s ‘cold adapted,’ as we call it, and cannot multiply at the slightly higher temperatures down in your lungs. So even that live, attenuated virus cannot give you the flu.”
Stinchfield said unequivocally, “It is not possible to get influenza from the flu vaccine.” She then added an artful analogy that being vaccinated is like practicing before a game or performance.
“When your kids are saying they don’t want to get the flu shot, tell them you practice for your sport, you practice for choir and band,” she said. “This is practice for your immune system. You give it a little bit of a vision ahead of time so when the real virus comes your way, your immune system is ready.”
The 2021-2022 influenza vaccine protects against four strains of flu, with immunity in place about two weeks after vaccination. However, the vaccine does not protect against other viruses, Walensky noted.
“So, it is not uncommon during respiratory season that someone would get the flu vaccine and a week later get a cold,” she said. “We need to make sure that people recognize that is not the flu vaccine.”
Regarding flu vaccine efficacy, the vaccine is made every year to match the circulating viral strains and sometimes it is more effective than others. However, even in an imperfect year, the flu vaccine can prevent hospitalization and death, Walensky said.
For example, a record 199 children died of flu during the 2019-2020 season in the United States. “Consistent with findings from other seasons, about 80% of those children were unvaccinated,” she said.
Co-Infection with Pandemic Virus
If flu returns in force, there also is the risk of co-infection with COVID-19, which could prompt a serious inflammatory immune response. The viruses can present with similar symptoms of fever, cough, and shortness of breath, but there are tests to discern between the two or identify a co-infection.
“I have seen a couple of cases who had both infections simultaneously,” said Jamie Rutland, MD, CEO of West Coast Lung in Newport Beach, CA. “Those individuals were taken care of at home, but when they presented to the ER (emergency room) they were positive for influenza A and SARS-CoV-2. The inflammatory response of the immune system is going to be activated, which, quite frankly, we are all afraid of.”
“It’s another reason to get vaccinated for both, and we may see a more co-infections because there will be more flu this year,” Schaffner said.
Either influenza or SARS-CoV-2 is a serious infection during pregnancy, so the safety of vaccines for both viruses was emphasized to protect mother and child. There also are effective antiviral treatments for influenza, and pregnant women were urged to contact their provider at the first sign of symptoms.
“It is really helpful to call early, because your oxygen level can’t go too low before it starts affecting the baby,” said Laura Riley, MD, obstetrician and gynecologist-in-chief at New York-Presbyterian. “So, we want to know if you are having those symptoms, even if they seem mild. Most pregnant women we don’t even test. If we think it’s flu, we are going to give you medicine. That’s how serious we take it.”
The early arrival of circulating RSV was unwelcome news to Riley, in part because there is no vaccine for the virus.
“As an obstetrician, when you hear RSV, you start to cringe,” she said. “RSV is particularly bad for newborns, so moms need to do whatever they can to protect them from every virus for which there is a vaccine.”
The CDC has rigorous safety systems in place for both flu and SARS-CoV-2, which, in terms of adverse events, allows detection of “needles in haystacks when they occur,” Walensky said. “We have seen extraordinary safety with the flu and COVID vaccines in pregnancy.”
There is some thought that the pandemic will change the way people respond to respiratory viruses, and measures, such as masking, social distancing, and avoiding crowded indoor settings, will become more common in future flu seasons. Given the social divide over COVID-19, all bets are off on people doing the right thing for the current flu season.
“There are probably two groups out there, one being the very careful who are following this thoughtfully,” Schaffner said. “The data from the NFID survey [indicate] that these people will put on masks and do a little more social distancing when they encounter influenza in their community. There are other folks, as we know, who are still pretty cavalier about influenza and probably won’t take those precautions.”
In addition to continuing to emphasize vaccination for both viruses, the utility of masking and other mitigation measures will be a recurrent public health message, particularly for those at high risk of complications if infected with either — or both.
“Remember the common foe is not one another and it is not the vaccine,” Riley said. “It is the disease. We need to unite.”
REFERENCE
- National Foundation for Infectious Diseases. 2021 National Survey: Attitudes about influenza, pneumococcal disease, and COVID-19. Published October 2021. https://www.nfid.org/2021-national-survey-attitudes-about-influenza-pneumococcal-disease-and-covid-19/
A possible severe influenza season is on the horizon, in part because COVID-19 shutdowns and precautions led to a historically low flu season in 2019-2020, said Rochelle Walensky, MD, director of the Centers for Disease Control and Prevention.
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