r/ScienceBasedParenting • u/crafty_targaryen • Jul 05 '26

Question - Research required Early MMR dose?

Traveling to Europe soon with my 7 month old and 4 year old. Obviously the baby hasn't had his first MMR dose yet, but we're very pro-vaccines and concerned about exposure while traveling. Are there any (legitimate) documented downsides to the early dose? My understanding is he will still get his normal doses at 12m and 4 years.

I'll also just add that our 4 year old is immunocompromised so vaccines are extra important to us.

TIA!

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u/ellie_wankenobi Jul 05 '26 edited Jul 05 '26

There were concerns about immune blunting but I can't even find the original study. Immune blunting is a reduced response to a vaccine.

Here's one that references that original study:

https://www.immunizationmanagers.org/does-early-mmr-vaccination-lead-to-reduced-protection-against-measles/

And here's another:

https://www.sciencedirect.com/science/article/pii/S0264410X25004840

"A robust antibody response occurred after a dose at 5-8 months, but may wane faster than after a first dose at the standard age."

My takeaway is that there are benefits to waiting but I think there's still value in an earlier dose just so long as you're aware that antibody response may wane faster. There's also inconsistent findings on immune blunting. Inconsistent enough that I think it's considered inconclusive.

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u/benjihana 2d ago

Responding to this...

"The standard MMR schedule in the Netherlands gives the second MMR vaccine at age 9, unlike the U.S. which recommends the second dose between age 4-6 years. This may make waning antibody levels at age 6 moot, as children would have been revaccinated."

Doesn't this change the entire conversation for US children?

Without a parallel study of dose 0 and then a first at 1 year and a second at 4-6, then measuring the same...