Emily Oster

2 min Read Emily Oster

Emily Oster

What Fall Vaccines Should We Get?

Flu, COVID, and RSV

Emily Oster

2 min Read

The fall brings many things — the start of school, cooler weather, pumpkins … and also illnesses. If you have a school-age child, they’re probably bringing illness home along with their macaroni necklaces and math tests. And even if your child isn’t making a transition to school, the fall is still the time when respiratory viruses pick up. 

We’re going to focus on the big three: RSV, the seasonal flu, and COVID. To set the stage, the pictures below show the time path, by age, of hospitalizations for these three viruses in the past 12 months (these data come from the CDC). From these, we can see a few things:

  • It’s clear why we talk about these viruses now — there is a big spike in the late fall and winter in illness.
  • The age path of the viruses differ a bit. All three show much higher illness rates for older adults. For RSV, there is also a large impact in the youngest children. The flu also shows a large impact in the child age groups; COVID has less impact on younger people. 
  • Finally, we have seen a summer COVID spike that is not there in the others. Flu and RSV are generally reliable winter viruses; COVID is somewhat less predictable.

I find these graphs interesting, but they do not suggest action. So with this as background, we can turn to approaches to protecting yourself from these viruses this season.

RSV

I’m starting with RSV here for two reasons. First, of these viruses, it’s the one that disproportionately impacts infants. Second, the immunization options are newer, so there are more updates.

Most people will get RSV many times in their life. For older children and healthy adults, it tends to manifest as a mild cold. The heavily affected groups are infants and older people. The goal of RSV immunization, therefore, is to protect these groups. I’m going to focus here on infants, but I will note that there is a vaccine for older adults for RSV that rolled out last year and that is highly recommended for adults over 65.

In the case of infants, the focus is on protecting them in their first RSV season — that is, their first year of life. For healthy children, RSV infection at older ages may make them sick but is very unlikely to result in hospitalization or death. For young infants, those are both possibilities.  

There are two great options for protecting infants in their first RSV season. The first is to give protection to the infant directly. Last year, the FDA approved an immunization called Beyfortus for infants in their first RSV season. This isn’t a vaccine; it’s a monoclonal antibody. The core idea is that the shot delivers antibodies directly, unlike a vaccine, which induces the body to produce its own antibodies. 

In randomized trials, run before approval, the immunization provided extremely good protection against RSV (about an 80% reduction in hospitalization and a 90% reduction in hospitalization with a need for oxygen). Within the past year, we’ve also started to get data from the real world on protection. Some of this comes from smaller studies run in the U.S., but I think the best evidence comes out of Spain. This study, published in The Lancet, compared RSV rates in 2023 — after widespread immunization — with prior years. It found almost a 70% reduction in the risk of RSV hospitalization and an almost 90% reduction in the need for supportive oxygen. These numbers are not surprising given the success in randomized trials, but it’s very helpful to see this in the real world (and to see that there were no significant adverse events). 

The other option for protection against RSV is vaccination during pregnancy. This approach uses another new vaccine, Abrysvo, which is approved for use in pregnancy and for older adults. This option is a true vaccine — it induces an internal immune response. In pregnancy, it is given between 32 and 36 weeks, which gives time for antibodies to develop, pass to the infant, and then persist through the first months of life.

The initial data from vaccine trials showed that this option was also very effective in preventing disease in infants: 82% efficacy over the first three months of life. Generally, you would use either this option or immunization of the infant, not both. 

In the first approvals, there was a concern that RSV vaccination in pregnancy might increase the risk of preterm birth, based on the observation that preterm birth rate was about 1 percentage point higher in the group that was vaccinated. Initial data from the real world, however, is more reassuring. This study, published in July 2024, uses data from New York State to compare preterm birth rates for women who had evidence of RSV vaccination during pregnancy with those who did not. The researchers found no signal of a higher preterm birth rate in the vaccinated group (the rates were actually lower, but not significantly so). 

Conclusion: Both immunization of infants after birth and vaccination during pregnancy are safe and effective approaches to RSV. If you’re expecting a baby or you have an infant who was born after the last RSV season (say, after January 2024), please consider one of these options to protect them.

Seasonal flu

The seasonal flu kills an estimated 15,000 to 25,000 Americans a year, mostly older adults. Flu strains vary over time, so each year there is a new seasonal flu vaccine, targeted to the current strain. The decision about which strain of flu to target is made in the spring, usually based on what strain is prevalent in the Southern Hemisphere at that time. The match of the vaccine to the flu strain varies over time, so efficacy varies. However, even if the vaccine isn’t perfectly matched to that year’s virus, it still provides some protection against serious illness.

From a parental standpoint, I think we learn the most about the flu vaccine from the work of Dr. Anupam (Bapu) Jena (here’s his book and a recent paper) at Harvard. What’s very helpful about this work is that Dr. Jena exploits a source of randomness in flu vaccination to generate causal estimates. He and his co-authors used the fact that flu vaccinations are typically given at well-child visits, which often happen around birthdays. This means that if your child has a birthday around the time the flu vaccine is available, they are more likely to get it. But since birthday month is otherwise unrelated to illness, the authors can use that fact to figure out how much the vaccine matters.

The upshot of this work is that flu vaccines do protect kids from getting the flu, as well as protecting elderly people who live with them from getting the flu and possibly getting very ill. This work has also revealed the best time to get the flu vaccine: October. August seems to be too early (the antibodies wear off before the meat of the flu season), and December is too late (there are already a lot of exposures).

Of course, vaccination at any time is better than never! Just, if you get to pick: October.

A note on pregnancy: This October timing recommendation goes for kids and adults (including older adults). If you are pregnant, there may be value to earlier vaccination if you are due in the fall. Ideally, you’d have at least four weeks between vaccination and birth, to give antibodies time to pass to the baby. That could mean vaccination now if you’re due in October.

COVID-19

COVID vaccines, at this point, mirror the flu vaccine. The vaccine is reformulated each year to match the best guess of the dominant strain. Although the strain chosen for the COVID-19 vaccine this year is not an exact match to the current dominant strain, it is close enough that the vaccine will provide protection. 

COVID vaccines have been reliably shown to lower risk of hospitalization, serious illness, and death. They have a more minimal impact on the risk of getting sick at all, and the impacts on transmitting to others are estimated to be limited. As a result, these vaccines are most valuable for individuals who are at serious illness risk from COVID. This means older people and those with a compromised immune system. 

The COVID vaccine is also recommended during pregnancy, both to provide protection to the infant and because in some waves of COVID, pregnant women have been especially affected. 

For healthy adults and children, there is more debate about COVID vaccine recommendations. The CDC recommends the seasonal COVID booster for everyone over six months, but other countries have taken a narrower approach. The U.K. is offering boosters only to those over 64, with immunocompromising conditions, or who work in places where they have a lot of contact with the elderly.

There are pluses and minuses to both approaches. The most important individual note here, though, is that if someone is 65 or over, and especially if they’re (say) over 80, they should get the COVID booster. For younger people and for kids, it is less urgent. Reasonable people will make different choices in this group.

Given this summer’s wave of COVID, it is also important to note here that if you’ve had COVID in the past four months or so, you do not need a booster.

A final note

Many kids are afraid of shots, and this can be a barrier to vaccines, like the flu vaccine, that may feel more “optional.” I love this book for working younger kids through what to expect and dialing down the fear. (Disclosure that I know the author, but I’m recommending the book because I think it’s perfect for this purpose.)

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Nicole RG
Nicole RG
2 days ago

You mention the COVID vaccine has limited effect for preventing transmission- is it still valuable for parents/siblings to get it to protect our 6 month old, or would it not have much effect on her risk?

Verob
Verob
18 days ago

You have mentioned in the COVID section that it’s not necessary to get a booster if you had Covid during the summer months. What if I don’t l know for sure? Does an antibody test make sense? Does this also apply for pregnant women or would you get the vaccine anyway?

Anastasia
1 month ago

The post says that generally it’s recommended to either get the RSV vaccine during pregnancy or get the infant vaccinated in their first RSV season. It also says that getting the vaccine during pregnancy is only shown to protect the infant in their first 3 months of life.

In my case, I got the RSV vaccine when 32 weeks pregnant with my child who was then born in April. Her 3 months of documented protection from RSV expired in July, and here we are almost in October on the cusp of RSV season.

My question is: should I still angle to get her her own vaccine now because my shot during pregnancy might no longer have any effect on her since she is now more than 3 months old (almost 6 months old, in fact)?

janellebrook
janellebrook
1 month ago
Reply to  Anastasia
1 month ago

It seems baby would be entering first RSV season this Fall as April is really at the end of the season, and thus be eligible. Pediatrician can advise!

Cartulina89
Cartulina89
1 month ago

My baby contracted RSV at 40 days old and ended up needing ECMO therapy. It was really, really bad—we’re incredibly lucky to still have her with us. She’s now 4 months old, and I’m wondering if she should get the Beyfortus or Abrysvo vaccine or if it’s unnecessary now that she’s already had RSV? (Also, a friendly reminder to all parents wondering whether to get the vaccine—please do! It’s definitely a virus you want to avoid.)

janellebrook
janellebrook
1 month ago
Reply to  Cartulina89
1 month ago

some babies who are entering their second season can get the monoclonal antibody, Beyfortus. There is no RSV vaccine for babies. Please talk to your pediatrician to see if your baby is eligible.

GLK27
GLK27
1 month ago

Is the Covid vaccine advice just for boosters or for the initial vaccine as well? I have a 7-month old and ped says basically what you do, that we could go either way about vaccinating him. What age should a child get the first Covid vaccine then? He will need it at some point right?

MMD
MMD
1 month ago

Is it worth asking older adult relatives who qualify for RSV vaccine to get it before seeing newborn? Or same advice to just not come around if sick? For reference I’m due in mid October and plan to have baby receive infant monoclonal antibody shot as I did not get the RSV vaccine myself.

hthr.rose
hthr.rose
1 month ago

I got the RSV vaccine at 36 weeks pregnant. I gave birth early at 10 days after this. My understanding is that you need to have two weeks for the vaccine to protect your baby in utero. Would my baby have gotten any protection within the 10 days prior to birth?

vhs216
vhs216
1 month ago

Is there any data around Covid vaccine decreasing the potential for long covid?

Socorro
1 month ago

Does anyone know when the Covid vaccine will be released for children over 3? I keep seeing articles saying it’s recommended by the CDC, but none of the pharmacies in my area have it or have information about when they will receive it (they have the adult vaccine). It’s always such a struggle to find places to get my kids the Covid vaccine, and I thought it would be easier this year now that they’re over 3.

HBrown
HBrown
1 month ago

Curious how long the flu and COVID vaccines last? Asking because of a Feb due date and want to make sure we both are covered!

jgabernathy
jgabernathy
1 month ago

So helpful – thank you! If I get the flu and Covid vaccines, will these benefit / help protect my breastfed 3 month old?

snipy
snipy
1 month ago

Very helpful info! TY! If your due date is this winter (i.e., early Dec ‘24), does the data provide any clarity whether it is more optimal for the mother to get the RSV vaccine while pregnant or the baby to get immunization after birth. For the sake of clarity, by more optimal I mean lower risk of adverse events and higher protection efficacy for the infant.

Ellie
Ellie
1 month ago

I’m due October 26. If I’m inferring correctly from your article, would the data suggest I get COVID and flu shots 4 or more weeks before my due date?

raluca.muja@gmail.com
raluca.muja@gmail.com
1 month ago
Reply to  Emily Oster
1 month ago

are flu shots actually available? I live in Switzerland and all doctors I asked said they don’t have this season’s flu shots yet. They expect them early November.

juleliz
juleliz
1 month ago

Does the October timing recommendation for the flu shot also apply to the COVID shot? Looks like hospitalizations peak around the same time, so I would assume yes, assuming the duration of the immunity is similar?

laurathere
1 month ago

Query: You’re saying that if you get the RSV vaccine in the later stage of pregnancy, you likely wouldn’t also give it to the infant. But what about if you’re due in, say, April? It seems like by the time the following RSV season rolls around, the baby would no longer have any protection from the vaccine the mom got while pregnant.

kash
kash
1 month ago
Reply to  Emily Oster
1 month ago

We gave baby the monoclonal right after they were born in the hospital early March of this year. Should he get it again considering he’s under 1 and entering his first RSV season?

janellebrook
janellebrook
1 month ago
Reply to  kash
1 month ago

There are guidelines for giving higher risk babies/toddlers another dose entering their second season. Pediatrician will know!

Amanda
1 month ago

Any views on which covid vaccine to get? Thoughts on whether there is still value to mix and match, or whether Novovax might have fewer side effects as has been anecdotally reported?

Burgh NP
1 month ago

Thanks for this, Emily! Just to clarify, the CDC updated its RSV vaccine guidance in June stating that adults over 75, and adults between 60 and 75 with certain chronic health conditions (including BMI over 40) should get the RSV vaccine.
The following is attributable to CDC Director Dr. Mandy Cohen:
“The CDC has updated its RSV vaccination recommendation for older adults to prioritize those at highest risk for serious illness from RSV,” said Mandy Cohen, M.D., M.P.H. “People 75 or older, or between 60-74 with certain chronic health conditions or living in a nursing home should get one dose of the RSV vaccine to provide an extra layer of protection.”

smsmauney
smsmauney
1 month ago

Is there a recommended best time for babies to get the RSV vaccine?

Kara
1 month ago

If you got the RSV vaccine while pregnant and had an April baby, should you do an rsv vaccine again this fall? It sounds like the benefits from the shot given in pregnancy only last a few months but also the article said you normally do one or the other not both rsv vaccines.

ES12
ES12
1 month ago
Reply to  Kara
1 month ago

I came here with the same question- got the vaccine while pregnant, had a March 2024 baby!

katherine.v.boyle@gmail.com
katherine.v.boyle@gmail.com
1 month ago
Reply to  ES12
1 month ago

Same here – February 2024 baby!

MEG
MEG
1 month ago
Reply to  Kara
1 month ago

Came with the same question! Due March 2025.

laurathere
1 month ago
Reply to  Kara
1 month ago

Ha oops I just asked the same question (due March next year).Guess it’s a common one!

kkh237@gmail.com
kkh237@gmail.com
1 month ago
Reply to  Kara
1 month ago

Same question here! @emily any chance we can get an addendum?

Amy Beth
1 month ago
Reply to  Kara
1 month ago

I just spoke to the pediatrician about this same question! They told me to call my insurance company and ask if my Feb 2024 baby would be covered. They gave me CPT code 96380, billing code 90381 and ICD Z29.11. I’m still waiting to hear back from my insurance company but thought I’d share that info!

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