“Tripledemic“ jumped into our vocabulary and lives last year, referring to the winter surges of three respiratory viruses—RSV (respiratory syncytial virus), flu (influenza), and COVID-19. The tripledemic of 2022 infected millions, overwhelmed hospital systems, and killed more than 100,000 people in the U.S. over the 4-month peak span of these viruses.
As much as we hoped that respiratory illness would fade with the COVID-19 public health emergency ending, we must recognize that these viruses will continue to impact us for years. As the school year begins, we already see short-term school closures due to respiratory illness. We are seeing new variants of COVID-19 that may also contribute to increased cases of disease.
However, the severe impact of the anticipated wave of respiratory illness this winter can be very different from last year. We can reduce the levels of severe viral disease seen over recent years, thanks to the remarkable development of new vaccines and therapeutics against these viruses. We can achieve this goal of preventing hospitalization and death by ensuring that individuals at the most significant risk for severe disease are vaccinated against each of these viruses before the late fall and winter months and receive prompt antiviral treatment when ill.
RSV, flu, and COVID-19 are respiratory pathogens spread by the breath, spoken word, and cough. As with most pathogens, some individuals are more vulnerable than others to these infections. RSV and influenza take their most significant toll on those less than one year and older than 65 years and in people with serious underlying medical conditions. COVID-19 also exerts its most severe impact on older people and those with underlying medical problems. Although less frequent than in adults, COVID-19 can also result in severe disease in children, more than 50% of whom have no underlying medical conditions, which is why COVID-19 vaccines are recommended for children six months and older by the American Academy of Pediatrics and the Centers for Disease Control and Prevention (CDC).
During the respiratory season of 2022-2023, it was estimated that 100,000-200,000 people were hospitalized with RSV, 300,000-650,00 with flu, and 700,000 with COVID-19. During that surge, 6,000-10,000 people died from RSV, 19,000-58,000 from flu, and 75,000 from COVID-19. These numbers of deaths due to RSV were greater than the levels seen over the several years before the pandemic. It was remarkable that RSV and flu-related illnesses fell over the first two years of the COVID-19 pandemic, partly due to the mitigation measures against COVID-19, which also slowed the spread of these other respiratory viruses. Yet, with the relaxing of masking and other anti-COVID-19 mitigation measures, RSV and flu cases rebounded to exceed pre-pandemic levels. It is difficult to predict the patterns of RSV, flu, and COVID-19 over the coming months. But we can expect a rise in the activity of these viruses as population immunity from last year's infections and vaccinations wanes and new viral forms appear.
This past year heralded important developments in the prevention of RSV. RSV infection among children under five years, which resulted in 58,000-80,000 hospitalizations and 100-300 deaths last year, can be prevented in several ways. If a pregnant individual is vaccinated against RSV, the transfer of immune protection from the parent to the fetus will protect the infant after birth, and such vaccines have recently been approved. If parents are not immunized against RSV during pregnancy, infants can receive a long-acting monoclonal antibody by injections to protect against severe disease for up to 6 months. This FDA-approved medication, Beyfortus, is now available through the Vaccines for Children (VFC) program and through pediatric care providers. The drug is approved for neonates and infants born during or entering their first RSV season and in children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season. RSV vaccines for those 60 years and older have also been approved, dramatically reducing cases in older people.
The influenza vaccine is modified yearly in anticipation of the expected flu strain and is recommended for those six months and older. The flu vaccine, with doses specific for children and adults, becomes available in the fall and comes in forms administered by injection or a nasal spray. This year’s vaccine is designed to target several different flu strains. In addition to vaccines, several anti-flu medications, including Tamiflu, effectively reduce flu severity if started within a few days of illness onset.
Although cases, hospitalizations, and deaths due to COVID-19 are much lower now than over the previous three years, this virus remains a serious public health threat, with more than 100,000 deaths over the current year. COVID-19 will also be a top-five cause of death for adults and a top-ten cause of death for children. As with RSV and flu, severe disease due to COVID-19 is preventable through vaccination.
For individuals who develop COVID-19 infections, disease severity can also be markedly reduced by oral antiviral agents, including Paxlovid and Mulnupiravir. More than 80% of adults in the US have received at least one dose of a COVID-19 vaccine, and 70% have completed the primary series. Because the protection from these vaccines phase after about six months, booster shots are recommended, but only 17% of the US population has a current booster shot. Like the flu vaccine, booster vaccinations are adapted to the anticipated circulating virus type, the Omicron variant. On September 12, 2023, the CDC recently recommended that everyone six months and older get updated COVID-19 vaccines from Moderna and Pfizer-BioNTech that better match the current circulating virus strains. These new vaccines will be available within a week of the announcement.
More than 700 million doses of COVID-19 vaccine have been administered in the U.S., and data clearly show that COVID-19 vaccines are very effective in reducing severe disease risk and have an excellent safety record, as shown in very recently presented data. Notably, the risk of myocarditis following last fall’s updated COVID-19 vaccine was minimal, with two confirmed myocarditis out of about 650,000 doses, which is lower than after the primary series.
There is recent discussion has been about when to get flu or COVID-19 booster shots. Because the effectiveness of the flu and COVID-19 vaccines can wear off after six months, it makes the most sense to get these vaccines in late October or November before the anticipated peak of illness during wintertime. Until there is a combination respiratory pathogen vaccine, these vaccines need to be administered separately. Flu and COVID-19 vaccines can be given simultaneously. Still, since the RSV vaccine is new, it has been recommended to wait two weeks after the RSV vaccine before other immunizations until more data are available.
Common sense public health measures also play a role in combatting the tripledemic, as we can spread viruses to others when we are infected. First, we must avoid others, especially those with vulnerabilities, when ill. We also now have home testing available to diagnose each virus separately or in combination. This can lead to prescribing antiviral medication and treating symptoms when coupled with telemedicine or in-person office visits. Mask use may also be considered in high-risk settings, especially for those who are medically vulnerable.
As part of this discussion of tripledemic action, we also need to recognize that issues related to COVID-19 have become politically polarized to the point where facts about the disease, its impact, its treatment, and its prevention are ignored. But we also need to recognize that COVID-19 now takes its place among the other common respiratory pathogens, and we have strong medical tools to address tripledemic viruses.
With all the amazing preventative tools and treatments we now have, we can look forward to saying, “tripledemic severe disease, no more.”
Correction, September 19: The original version of this story misspelled the monoclonal antibody developed by Sanofi and AstraZeneca.
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