COVID-19, RSV and the flu: What the ‘triple threat’ means for children
Rebecca S.B. Fischer, Assistant Professor of Epidemiology, Texas A&M University, and Annette Regan, Assistant Professor of Epidemiology, University of San Francisco
Every fall and winter, viral respiratory illnesses like the common cold and seasonal flu keep kids out of school and social activities. But this year, more children than usual are ending up at emergency departments and hospitals.
Pediatric emergency rooms in some states are at or over capacity due to the surging number of respiratory infections. GOLFX/iStock via Getty Images Plus
In the U.S., the winter respiratory virus season started earlier than usual this year. Since peak infections usually occur in late December or January, this uncharacteristic early wave suggests that the situation could get much worse for people of all ages, particularly children.
We are epidemiologists with expertise in epidemic analysis for emerging disease threats, including respiratory infections. We watch patterns in these infections closely, and we pay particular attention when the patterns are unusual. We’ve grown increasingly concerned about the amount of pediatric hospitalizations over the last few months and the pattern that is emerging.
The ‘triple threat’
In early November, the Centers for Disease Control and Prevention issued a health advisory about increased activity in respiratory infections — especially among children. The CDC and other health experts are warning of the so-called “triple threat” of respiratory illness from RSV, influenza — or the seasonal flu — and COVID-19.
The underlying reasons for the convergence of these viruses and the increase in infections so early in the season are not yet clear. But health experts have some clues about contributing factors and what it could mean for the coming months.
As of mid-November 2022, a children’s hospital in Buffalo, N.Y., had already admitted more than double the number of respiratory syncytial virus patients than in the entire 2019-2020 respiratory season.
When it comes to COVID-19, 2022 is expected to usher in another winter wave of infections, similar to patterns seen in 2020 and 2021. Previous winter surges stemmed from a combination of factors, including the emergence and spread of new viral variants, more people gathering indoors rather than distanced outside, and people coming together for the holidays.
But unlike previous pandemic winters, most COVID-19 precautions — such as using masks in public areas or avoiding group activities — are more relaxed than ever. Together with the looming threat of new variants, it is difficult to predict how big the next COVID-19 wave could be.
And while the seasonal flu has proved somewhat unpredictable during the COVID-19 pandemic, it nearly always hits during late October. Flu season also arrived about a month early and in greater numbers than in recent history. By our read of the data, pediatric flu hospitalizations are nearing 10 times what has been seen for this time of year for more than a decade.
RSV infections tend to follow a similar seasonal pattern as the flu, peaking in winter months. But this year, there was an unexpected summer wave, well before the start of the typical fall respiratory virus season.
In typical years, RSV garners little media attention. It’s incredibly common and usually causes only mild illness. In fact, most children encounter the virus before age 2.
But RSV can be a formidable respiratory infection with serious consequences for children under 5, especially infants. It is the most common cause of lower respiratory infections in young children, and more severe illnesses can lead to pneumonia and other complications, often requiring hospitalization.
One reason the youngest children are at greater risk is that their immune systems are not yet fully developed and don’t produce the robust immune response seen in most adults. What’s more, infants younger than 6 months — who are most at risk of severe disease — are still too young to be vaccinated against influenza or COVID-19.
These viruses present challenges on their own, but their co-circulation and coinciding surges in infections create a perfect storm for multiple viruses to infect the same person at once. Viruses might even act together to evade immunity and cause damage to the respiratory tract.
There are a few reasons why the U.S. may be seeing a surge in pediatric respiratory infections. First, COVID-19 protection strategies actually help prevent the transmission of other respiratory pathogens. School and daycare closures likely also minimized exposures children normally have to various respiratory viruses.
These and other efforts to prevent the spread of COVID-19 seem to have suppressed the broad circulation of other viruses, including influenza and RSV. As a result, the U.S. saw an overall drop in non-COVID respiratory infections — and an almost nonexistent flu season in the winter of 2020.
The early surge of respiratory infections underscores the need to get children up to date on flu and COVID-19 vaccinations. Geber86/E+ via Getty Images
The decreased viral activity means that children missed out on some exposures to viruses and other pathogens that typically help build immunity, particularly during the first few years of life. The resulting so-called “immunity debt” may contribute to an excess of pediatric respiratory infections as we continue into this season.
To further complicate the picture, the changing nature of viruses, including theemergence of new COVID-19 variants and the natural evolution of seasonal influenza viruses, means that we could be seeing a unique combination of particularly transmissible strains or strains that cause more severe illness.
Proactive steps people can take
The early surge in respiratory infections with high rates of hospitalization highlights the importance of prevention. The best tool we have for prevention is vaccination. Vaccines that protect against COVID-19 and influenza are available and recommended for everyone over 6 months of age. They have been shown to be safe and effective, and they can and do save lives.
The best way to protect infants younger than 6 months old against flu and COVID-19 is by vaccination during pregnancy. When a pregnant mother is vaccinated, maternal antibodies cross the placenta to the baby, reducing the risk of COVID-19 hospitalization in young infants by 61%. Vaccination of other caregivers, family and friends can also help protect infants.
Other preventive measures, like hand-washing, covering sneezes and coughs, staying at home and isolating when sick, can help to protect the community from these viruses and others. Paying attention to local public health advisers can also help people to have the most up-to-date information and make informed decisions to keep themselves and others — of all ages — safe.
Rebecca S.B. Fischer receives funding from the Fogarty International Center at the U.S. National Institutes for Health and has previously received research funding from the National Institute for Allergy & Infectious Diseases.
Annette Regan currently receives funding from the National Institutes for Health and the US Centers for Disease Control and Prevention. She has previously received research funding from the National Health and Medical Research Council (Australia), HRSA’s Federal Office of Rural Health Policy, the Wesfarmers Center for Vaccines and Infectious Diseases, and the EuroQol Research Foundation.
This article is republished from The Conversation under a Creative Commons license.
How the flu shot is determined each year
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Millions of people get the flu every year during flu season, which is primarily during the fall and winter months with December through February being the peak point. Infection with the influenza virus, commonly known as the flu virus, can lead to all manner of symptoms from fever and congestion to fatigue or respiratory issues.
But while some people experience flu infection as little more than a "rough cold," the flu is a potentially serious illness. Complications from the flu can lead to hospitalization or even death—especially for older people, very young children, and those with chronic health conditions like heart disease, asthma, or diabetes.
The best way to reduce your risk of getting the flu is to get an annual flu shot. All flu vaccines available in the U.S. are quadrivalent, meaning they have been engineered to protect against four different strains of influenza. The Centers for Disease Control and Prevention recommends that, with few exceptions, anyone aged 6 months or older get vaccinated against the flu with either a direct injection vaccine or an attenuated vaccine, which is administered as a nasal spray.
Millions of people get the flu every year during flu season, which is primarily during the fall and winter months with December through February being the peak point. Infection with the influenza virus, commonly known as the flu virus, can lead to all manner of symptoms from fever and congestion to fatigue or respiratory issues.
But while some people experience flu infection as little more than a "rough cold," the flu is a potentially serious illness. Complications from the flu can lead to hospitalization or even death—especially for older people, very young children, and those with chronic health conditions like heart disease, asthma, or diabetes.
The best way to reduce your risk of getting the flu is to get an annual flu shot. All flu vaccines available in the U.S. are quadrivalent, meaning they have been engineered to protect against four different strains of influenza. The Centers for Disease Control and Prevention recommends that, with few exceptions, anyone aged 6 months or older get vaccinated against the flu with either a direct injection vaccine or an attenuated vaccine, which is administered as a nasal spray.
Vaccination is not a guarantee against illness, but it is a strong deterrent. Aside from helping the body build immunity to the influenza strains most likely to circulate in a given flu season, the flu vaccine can reduce the severity of the illness and risk of hospitalization should a person get sick despite being vaccinated.
The vaccine can also protect against serious complications arising from the flu for people with chronic conditions such as diabetes, chronic obstructive pulmonary disease, or heart disease. Flu vaccines can also protect pregnant women during pregnancy and their newborns during the first few months of life. Vaccination also works to limit the spread of the flu virus should an infected person come in close contact with others while contagious.
Canva
Vaccination is not a guarantee against illness, but it is a strong deterrent. Aside from helping the body build immunity to the influenza strains most likely to circulate in a given flu season, the flu vaccine can reduce the severity of the illness and risk of hospitalization should a person get sick despite being vaccinated.
The vaccine can also protect against serious complications arising from the flu for people with chronic conditions such as diabetes, chronic obstructive pulmonary disease, or heart disease. Flu vaccines can also protect pregnant women during pregnancy and their newborns during the first few months of life. Vaccination also works to limit the spread of the flu virus should an infected person come in close contact with others while contagious.
All flu vaccines administered in the U.S. are quadrivalent vaccines. They provide protection against four unique flu viruses: an influenza A(H1N1) virus, an influenza A(H3N2) virus, and two influenza B viruses.
The intravenous flu shot and the nasal spray flu vaccine are both typically produced by growing candidate vaccine viruses in fertilized hens' eggs and then purifying the viral antigen—or the virus particles that help the immune system mount its response to the virus. A flu vaccine can also be made by growing candidate viruses in mammalian cells and then purifying the viral antigen. The intravenous flu shot is an inactivated (or "killed") vaccine, containing dead strains of the viruses, while the nasal spray is a live attenuated vaccine, meaning the flu strains are alive but in weakened doses.
The egg-based process has been relied on by antivirus developers for more than 70 years, whereas the cell-based process was only approved by the Food and Drug Administration in 2012. The advantage of the mammalian cell-based process is that it is much swifter than the egg-based process and is not contingent on there being enough eggs available for mass production.
A third development process, which uses recombinant technology, was approved by the FDA in 2013. Recombinant flu vaccines are manufactured without hens' eggs or mammalian cells and do not require candidate viruses. To produce recombinant flu vaccines, scientists first isolate the gene containing instructions for making the protein hemagglutinin, which is found on the surface of a flu virus and helps the immune system produce antibodies against the virus. Scientists insert this gene into a baculovirus, a virus that infects invertebrates. This baculovirus transports the instructional gene into a host cell line and instructs the host cells to produce hemagglutinin. The hemagglutinin is then collected, purified, and made into a recombinant flu vaccine.
For the 2022-2023 flu season, while the CDC makes no specific recommendation for which flu shot persons under the age of 65 should seek, it does recommend three different high-dose vaccines as best for those over 65.
Canva
All flu vaccines administered in the U.S. are quadrivalent vaccines. They provide protection against four unique flu viruses: an influenza A(H1N1) virus, an influenza A(H3N2) virus, and two influenza B viruses.
The intravenous flu shot and the nasal spray flu vaccine are both typically produced by growing candidate vaccine viruses in fertilized hens' eggs and then purifying the viral antigen—or the virus particles that help the immune system mount its response to the virus. A flu vaccine can also be made by growing candidate viruses in mammalian cells and then purifying the viral antigen. The intravenous flu shot is an inactivated (or "killed") vaccine, containing dead strains of the viruses, while the nasal spray is a live attenuated vaccine, meaning the flu strains are alive but in weakened doses.
The egg-based process has been relied on by antivirus developers for more than 70 years, whereas the cell-based process was only approved by the Food and Drug Administration in 2012. The advantage of the mammalian cell-based process is that it is much swifter than the egg-based process and is not contingent on there being enough eggs available for mass production.
A third development process, which uses recombinant technology, was approved by the FDA in 2013. Recombinant flu vaccines are manufactured without hens' eggs or mammalian cells and do not require candidate viruses. To produce recombinant flu vaccines, scientists first isolate the gene containing instructions for making the protein hemagglutinin, which is found on the surface of a flu virus and helps the immune system produce antibodies against the virus. Scientists insert this gene into a baculovirus, a virus that infects invertebrates. This baculovirus transports the instructional gene into a host cell line and instructs the host cells to produce hemagglutinin. The hemagglutinin is then collected, purified, and made into a recombinant flu vaccine.
For the 2022-2023 flu season, while the CDC makes no specific recommendation for which flu shot persons under the age of 65 should seek, it does recommend three different high-dose vaccines as best for those over 65.
There are four main criteria that help determine the direction research bodies will take in determining each year's vaccine: finding out which flu strains are making the most people ill in advance of a coming flu season and the degree of severity of those illnesses; the extent of those strains' spread; how successful the prior year's vaccine has been against those strains; and the ability of existing vaccine viruses to offer protection against a wider range of related viruses.
Members of the World Health Organization Global Influenza Surveillance and Response Team test thousands of samples from around the world. For human seasonal flu evaluation, samples are filtered through the WHO's Collaborating Centers for Influenza. The WHO then meets with the directors of the seven Collaborating Centers, along with WHO essential regulatory laboratories and thought leaders from national regulatory agencies to determine the composition of flu vaccines for the flu season in the Northern Hemisphere (which is done in February) and for the Southern Hemisphere (in September).
Scientists review data from clinical and laboratory studies, including epidemiological data that indicates what flu viruses are circulating and where; genetic data about the genomes of these circulating viruses; and antigenic data so the scientists can determine if vaccine virus-induced antibodies can effectively target circulating viruses. The CDC also tests serum from human blood after vaccination to see how well the antibodies from the flu vaccine neutralize circulating viruses.
Countries are then given the WHO's recommendations and determine for themselves which viruses to include in the coming season's vaccine for their respective populace.
Canva
There are four main criteria that help determine the direction research bodies will take in determining each year's vaccine: finding out which flu strains are making the most people ill in advance of a coming flu season and the degree of severity of those illnesses; the extent of those strains' spread; how successful the prior year's vaccine has been against those strains; and the ability of existing vaccine viruses to offer protection against a wider range of related viruses.
Members of the World Health Organization Global Influenza Surveillance and Response Team test thousands of samples from around the world. For human seasonal flu evaluation, samples are filtered through the WHO's Collaborating Centers for Influenza. The WHO then meets with the directors of the seven Collaborating Centers, along with WHO essential regulatory laboratories and thought leaders from national regulatory agencies to determine the composition of flu vaccines for the flu season in the Northern Hemisphere (which is done in February) and for the Southern Hemisphere (in September).
Scientists review data from clinical and laboratory studies, including epidemiological data that indicates what flu viruses are circulating and where; genetic data about the genomes of these circulating viruses; and antigenic data so the scientists can determine if vaccine virus-induced antibodies can effectively target circulating viruses. The CDC also tests serum from human blood after vaccination to see how well the antibodies from the flu vaccine neutralize circulating viruses.
Countries are then given the WHO's recommendations and determine for themselves which viruses to include in the coming season's vaccine for their respective populace.
One such myth is that flu vaccines can give you the flu. The vaccines are made from virus particles that are either inactivated (killed) or attenuated (weakened) so they cannot cause illness. While it is possible to catch the flu even if you are vaccinated, the vaccine itself is not the culprit.
Another misconception is that getting vaccinated twice can provide added immunity. Research has found no additional benefit from getting more than one flu vaccine during the same flu season. Getting more than one flu shot is also not recommended because there are some areas where vaccine shortage can lead to those in need having a difficult time getting their shot, a circumstance also seen widely in the early months of the initial COVID-19 vaccine rollout.
The COVID-19 pandemic gave rise to another false idea, namely that getting vaccinated against the flu increases one's risk of getting COVID-19. No scientific evidence exists to support this belief. One widely circulated study from 2020 seemed to suggest that this was, in fact, the case, but has since been debunked.
Finally, the idea that it is better to get sick with the flu than to get vaccinated is both untrue and potentially dangerous. The flu can be a particularly serious illness, especially for young children, those who are older, or people who have certain chronic conditions. It is much safer to get vaccinated than risk getting sick with the flu and lacking the immunity strength to combat it.
One such myth is that flu vaccines can give you the flu. The vaccines are made from virus particles that are either inactivated (killed) or attenuated (weakened) so they cannot cause illness. While it is possible to catch the flu even if you are vaccinated, the vaccine itself is not the culprit.
Another misconception is that getting vaccinated twice can provide added immunity. Research has found no additional benefit from getting more than one flu vaccine during the same flu season. Getting more than one flu shot is also not recommended because there are some areas where vaccine shortage can lead to those in need having a difficult time getting their shot, a circumstance also seen widely in the early months of the initial COVID-19 vaccine rollout.
The COVID-19 pandemic gave rise to another false idea, namely that getting vaccinated against the flu increases one's risk of getting COVID-19. No scientific evidence exists to support this belief. One widely circulated study from 2020 seemed to suggest that this was, in fact, the case, but has since been debunked.
Finally, the idea that it is better to get sick with the flu than to get vaccinated is both untrue and potentially dangerous. The flu can be a particularly serious illness, especially for young children, those who are older, or people who have certain chronic conditions. It is much safer to get vaccinated than risk getting sick with the flu and lacking the immunity strength to combat it.
Pediatric emergency rooms in some states are at or over capacity due to the surging number of respiratory infections. GOLFX/iStock via Getty Images Plus
The early surge of respiratory infections underscores the need to get children up to date on flu and COVID-19 vaccinations. Geber86/E+ via Getty Images
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