COVID-19 vaccine information

***For established patients only***

Is the new vaccine (2023-2024) recommended for my child?

IMPORTANT: this discussion only applies to children, the risks/benefits in adults may be quite different.

Summary and recommendations

• We continue to recommend a primary vaccination series for all unvaccinated children, using the most up-to-date strain (currently 2023-2024). We also recommend a booster with this new strain for children with any high-risk medical conditions. The evidence and consensus in support of these recommendations are high. While we would ideally like to see updated clinical trials with the new strain for the highest degree of confidence, it is most likely that the benefits will continue to far outweigh the risks in these situations.

• We are also offering the new booster to healthy, vaccinated children in alignment with the ACIP recommendations—in all likelihood the benefits, small as they may be, probably outweigh risks. However, due to the lack of clinical trials, less scientific consensus, and possibly quite small observed benefit, we are not going so far as to say we recommend all vaccinated children must get a new booster, nor would we recommend against it. We feel that each family needs to take into account your situation and values, your child’s health, how well they tolerate shots, risk of exposure, and how disruptive a COVID illness would be to your family vs. how disruptive getting a shot is. See discussion below for more details.

Details and explanation

The answer differs whether we are talking about a primary series (for those unvaccinated with any COVID vaccine) or if we’re talking about booster doses for those who’ve already completed a primary series.

Primary series: Vaccination with a primary series is recommended for all children ages 6 months and up. All primary series will be completed with the new 2023-2024 formulation (see details below on safety and effectiveness). There is strong data and scientific consensus that primary vaccination reduces hospitalization, severe illness, and complications from COVID infection in children. This benefit is in addition to natural immunity, so the hybrid combination of vaccine immunity + natural immunity together are better than either alone. Even healthy children are at risk from complications due to COVID, and it is worth mitigating that risk with a vaccine that has demonstrated a very good safety profile, with far fewer risks than the illness itself. For infants less than 6 months old, those around them (parents, caregivers) should receive the vaccine to protect the infant until they are old enough to get their own vaccine.

Booster doses: Once vaccination with a primary series has been complete, the additional benefit conferred from booster doses is less certain. The remainder of this page will focus on this issue, though it will also include some safety information about the current vaccine relevant to those using it for their primary series.

Firstly, children at high risk of complication from COVID should get the booster dose (such as heart disease, obesity, diabetes, infants with prematurity, airway abnormality or significant genetic/developmental/neuromuscular conditions). Even if the additional benefit may be small, the vaccine has been well tolerated and any potential benefit in such high risk cases would be worth it.

For healthy, vaccinated children without any high-risk medical conditions, there is less consensus on how much difference an additional booster dose will make. To be clear, the Advisory Committee on Immunization Practices (ACIP) at the CDC recommends this booster to all children ages 6 months and up. However, this time it’s a bit different as the ACIP’s vote was not unanimous, though it did pass. The recommendation also differs from that of the World Health Organization and even the eminent vaccine advocate Paul Offit. Here are some of the reasons why there is not as much consensus about booster doses in healthy children:

• Serious illness and hospitalization in children appear to be effectively reduced by primary vaccination from any series combined with wild type immunity from ongoing exposure. We have no conclusive evidence at this time how much these outcomes could be improved with another booster, with at least some evidence suggesting it might not be. Most children hospitalized from COVID were simply not vaccinated at all. Basically, immunity doesn’t need to be a perfect match to prevent the more severe outcomes.

• As for milder illnesses, to prevent an infection from occurring at all you need a much closer match. But COVID’s rapid mutation, huge diversity of strains, and lack of a predictable pattern make this challenging. The Catch-22 is that boosting too frequently generates a weaker immune response. But if we wait longer, say a year, for a more robust immune response, so many will have already been exposed that it may render the booster moot. Even among the unexposed, only if they were then going to actually fall ill from a covered strain within an ideal window after vaccination would they experience the full benefit. Otherwise, immunity wanes and the strain could fade from prevalence in a few months.

  These factors don’t necessarily make getting a booster pointless, they just make the actual benefits a child might experience less than a booster’s theoretic effectiveness would imply. For some kids the timing may work in their favor, and it’s also possible there could be a small reduction of both mild and severe illness for all kids even when the timing isn’t ideal. Even a small potential benefit probably outweighs the even smaller risks of the vaccine. So the question isn’t as much do the benefits outweigh the risks, but rather if that is by a large enough margin to exceed your threshold for coming in and giving your child a shot.

How many strains of COVID are there, and how well does the current vaccine protect against them? The helpful graph below shows the immense variation of strains in circulation, and how impressively quickly it changes over time. When the strain for the current booster was selected back in June, it was by far the most prevalent strain (purple, XBB.1.5 on the far left). But already by the time this vaccine is now ready to administer, that strain is down to < 2%. That doesn’t mean it’s ineffective—it was shown to also induce antibodies for several other current strains, including EG.5. But it goes to show how broad a vaccine would need to be and how frequently it would need to be updated in order to have a huge impact on mild illness.

What safety and efficacy data is there for the current 2023-2024 booster?

We do not yet have as much safety and efficacy data as previous vaccines, and no clinical trials in children yet. Most of the safety and efficacy is extrapolated from previous versions of the vaccine, for which there is ample data. After updating the strain, Moderna demonstrated the new vaccine can produce neutralizing antibodies both in mice and in 50 adults against currently circulating strains. On average, side effects were better than previous vaccines.

Typically, when there are minor changes to a proven vaccine, and it produces the antibodies desired, it’s unlikely that it will differ significantly from prior versions in terms of safety or effectiveness. There is a small risk that a different antigen could trigger an unwanted immune response, though this is rare. All vaccines undergo very close post-marketing surveillance to monitor for such a possibility just in case. But if we waited until a large trial with 100,000 children and adults could be observed over a long enough period, that strain would no longer be in circulation by the time you had the answer, so that really isn’t a feasible option.

In summary, it's usually a pretty safe bet that an updated vaccine will be as well tolerated and effective as previous versions, even without new clinical trials in children. That makes it fairly easy to recommend in settings where we know the benefits are substantial, as with the primary series. But it’s a bit more of a barrier to decisively recommending it where the benefits aren’t yet proven—continuing to boost healthy, vaccinated children—at least until the benefits of that approach are better established.

We hope this information is useful.

Last updated 9/15/2023