An infectious disease expert at Rutgers Health explains the importance of getting crucial shots this fall
Between Oct. 1, 2023 and June 15 of this year, about 35 million to 65 million people contracted the flu, with hundreds of thousands hospitalized and 25,000 to 72,000 deaths, including 197 children, according to the U.S. Centers for Disease Control and Prevention (CDC).
The CDC also estimates that in 2023 more than 916,300 people were hospitalized for COVID-19 and about 75,500 people died.
Mid-September to late October is the optimal window for people to receive the updated flu and COVID-19 vaccinations to protect against severe illness this fall and winter, said David Cennimo, an infectious disease expert at Rutgers New Jersey Medical School.
Cennimo discusses what you need to know about the series of recommended vaccines as well as what to anticipate this season for respiratory syncytial virus (RSV).
What can we learn from last year’s flu season – and what should we expect this year?
The 2024-2025 influenza season is again predicted to peak sometime between late fall and early spring. The southern hemisphere influenza season is ending now and may provide some clues and predictions for the U.S. Most countries had similar levels to last season with severe disease also being seen. Unfortunately, a few countries did have much higher activity than expected. Most experts believe we will see similar levels of influenza infection as last year in the United States.
Who should receive a vaccination for flu and COVID-19?
The CDC recommends that people 6 months and older receive vaccinations for the flu and COVID-19. It is safe to receive both vaccines at the same visit.
Multiple studies have demonstrated significantly reduced symptoms and a milder infection in vaccine recipients who become infected.
David Cennimo
Rutgers New Jersey Medical School
What strains/variants will this year’s vaccines cover?
The 2024-2025 U.S. flu vaccine is trivalent, meaning that it contains three different strains of influenza predicted to be most like what will be seen this year.
Past years have been quadrivalent – four stains – however, the Yamagata lineage of Influenza B has not been seen in circulation since COVID-19 and has been removed. Slightly different virus strains are used for the egg-based vaccine versus cell culture-based vaccines. These changes address the ability of the virus to replicate and provide the best vaccine. At the individual patient level, they are interchangeable. The only advice I routinely give related to the specific type or brand of vaccine is for people 65 or older to attempt to get a “high dose” or adjuvanted flu shot. These stimulate more response in older immune systems. However, if they are not available, a standard influenza vaccine should be given.
Multiple studies have demonstrated significantly reduced symptoms and a milder infection in vaccine recipients who become infected.
The U.S. Food and Drug Administration approved an updated version of the vaccine that targets the SARS CoV-2 currently circulating in the U.S. Much like the yearly adjustment of the influenza vaccine, the COVID-19 vaccine was adjusted to best reflect the subtype of virus currently causing most infections.
How long should a person wait to be vaccinated after contracting COVID-19?
The minimum recommended time between COVID-19 vaccine doses is eight weeks, according to the CDC. Those with recent infection may consider delaying vaccination for three months. There is a lower risk of reinfection in the three months following a COVID-19 infection, regardless of symptoms, so people can be considered relatively protected. Based on the revaccination data, I would wait at least eight weeks.
Is RSV a concern this year?
Respiratory syncytial virus (RSV) is a common respiratory virus that usually causes mild, cold-like symptoms. The CDC recommends that infants 8 months and younger during RSV season receive an RSV immunization unless their mother was adequately vaccinated during the pregnancy. Older babies with certain medical conditions – in their second RSV season – may remain at high risk for complications from RSV infection and may require a second immunization.
Adults ages 60 to 74 with increased risk of severe RSV infection and everyone 75 or older should consider be vaccinated with one of three available RSV vaccines. Pregnant people should consider being vaccinated with the Abrysvo vaccine between 32- and 36-weeks gestation. Currently, RSV vaccines are only recommended for a one-time dose.
Why is mid-September to late October the best time to receive these vaccinations?
The influenza vaccine is effective for about six months, so if you get vaccinated too early there is a chance your immunity might wane. Children receiving their first influenza vaccine need a second dose at least four weeks later. Check with your doctor. The RSV season varies but usually starts in fall and the rates of COVID-19 tend to increase in fall winter.
Since RSV season starts in October, vulnerable people should receive the vaccine as soon as possible.
Are these vaccines safe?
Extremely rare side effects – like allergic reaction – can happen, but the risk is still lower than with many other common medications. You can get a flu shot even if you are allergic to eggs. Serious reactions to the small amount of egg protein in flu vaccines are unlikely.
Can you get the flu, COVID or RSV from the vaccine?
These vaccines take two weeks to be effective, so people still could contract these viruses during this period. COVID-19 vaccines contain no live virus so there is no way to become infected from the vaccine. With the flu vaccine, live viruses are grown but killed so there is no possibility of infection after vaccination, either.
How can I tell if I have the flu, COVID-19 or RSV?
Flu symptoms can be confused with COVID. If you start feeling ill, it is important to quarantine and test for COVID to rule it out.
The symptoms for RSV are like the common cold. They tend to run their course with only mild intensity in adults and older children. In infants and the elderly, symptoms tend to be more severe and can include fevers and wheezing.
