Will we vaccinate our four-year-old with Moderna? (Yes!)

Moderna is moving forward and the data are likely even better than most people realize.

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The big news is that Moderna finally submitted data on its pediatric Covid-19 vaccine to the Food and Drug Administration today. This comes over a month after the company first announced favorable results from their clinical trial that covered children ages 6 months to 6 years.

Let me not bury the lede: assuming the data look as good as we’ve been told, my 4-year-old child will be vaccinated with Moderna’s vaccine as soon as humanly possible.

We haven’t seen the actual data, but Moderna announced that its vaccines were 51% effective against symptomatic Covid-19 for children ages 6 months up to 2 years, and 37% effective for children ages 2 to 6.

The difference may be a matter of dosing. All of the children in the trial received the same dose (one-quarter of the adult dose), and that likely explains why the effect was better in the littlest ones. While correct vaccine dosing is probably not quite as tightly linked to weight as pediatric medications are, there’s still a relationship. So, a 25-microgram dose probably elicits a greater response from a 15-pound kid than it does from a 50-pound kid.

To some, Moderna’s efficacy numbers might sound a little ho-hum. But there are two reasons I am optimistic—and if you’ve been reading me for a while, you know that I’ve not given a free pass to vaccines that are found to be safe but insufficiently effective. (Wow, did I take heat for saying I would not vaccinate my then 3-year-old child with two doses of Pfizer that had been shown to be safe but not effective. Ultimately, I know my stance was the right one; even Pfizer eventually agreed, and delayed submitting its application for emergency use authorization of its vaccine for children under 5 until data on the efficacy of a 3-dose series become available.) So, you know that if I’m optimistic on this, it’s a very good sign. I don’t just go with the flow; I go with the data.

Let’s dig in. First, that the vaccine decreased symptomatic Covid-19 by 51% in the youngest group (and even 37% in the somewhat older group) is substantial. We just got spoiled by the results from the adult trials, conducted in the pre-Delta and pre-Omicron eras, in which efficacy against infection was often in the 80%–90% range, at least initially.

But the reality is that these vaccines are performing as intended; they generate an immune response that protects against long-term consequences, and those effects appear to be far more robust and longer lasting than protection against infection itself. The fact that Moderna’s new data aren’t as eye-popping also reflects the fact that a lot of the cases occurred during the Omicron wave. We know that Omicron is good at evading vaccine-derived protection against infection. So, to me, these findings were not a big surprise. If anything, I’m just glad the vaccines were found to protect against Omicron infection at all.

What we are really watching for is protection against severe disease and long-term consequences. Ironically, that is why what matters in the pediatric trials is antibody levels, not the efficacy against any infection. Now, in general, I prefer clinical outcomes as opposed to proxy data when we analyze data; that is, I care “How did the kids fare?” not “What were their antibody levels?” The former is a measurement of disease, while the latter measures something in the blood. If antibody levels were sky-high but people were dying left-and-right of Covid despite vaccination, would those antibody levels have any meaning? No. Moderna set out to study antibody levels. They achieved their pre-specified goals. They did not move the goalposts. This is called a success.

Indeed, we know that antibody levels do have meaning in Covid-19 vaccine studies. The concept is called “immune bridging,” and it has been a triumph for Pfizer in older children. The idea is that severe Covid-19 is common enough in adults that we can correlate favorable outcomes among the vaccinated to vaccine-induced antibody levels that were measured during the trials. If children are subsequently found to have similar antibody levels, we can infer that they will have the same protection. This is crucial because, thankfully, severe disease is less common among kids. Because of that, the trials aren’t big enough to detect a difference. The researchers knew this going in, which is why, for children, antibody levels were always the primary focus. What we have been told by Moderna is that the antibody levels they aimed for were achieved in the latest pediatric study. That tells me that kids who get the vaccine will gain the protection we want them to have.

As with older kids, we won’t know whether that works out until after the vaccines are authorized and administered to millions of kids. However, for children ages 5 and up, the strategy has worked splendidly so far. In large observation data-sets gathered after the vaccines were authorized, we’ve seen that hospitalization and other feared outcomes (such as multi-system inflammatory syndrome in children, or MIS-C) have been far lower among vaccinated kids.

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While it may not be the most popular viewpoint, I’m pretty sure my child will get infected with SARS-CoV-2 at some point. Whether she gets Covid-19—which is technically defined as infection and the symptoms it causes—is another matter. I think vaccines can reduce the likelihood that she will get sick at all. And the data we’ve been given so far indicate that they will markedly reduce the likelihood of any serious outcome. That’s what I’m looking for as a parent.

A question that people have been asking is whether it might make sense to wait for the Pfizer data. What if Pfizer’s three-dose series for the smallest children turns out to be demonstrably superior to the two-dose series that Moderna is moving forward with? The problem is that we just don’t know, and we might not know for some time. It’s conceivable that the three-dose Pfizer series might generate a better response initially, but quickly fade (it’s a lower dose, and that could affect things). So, unless Pfizer comes out with data in the next month or so (while the FDA assesses Moderna’s data) that absolutely blows Moderna out of the water, we plan to vaccinate our now 4-year-old child with Moderna as soon as the FDA authorizes it (assuming I agree with their data assessment). I want my child protected against serious outcomes as soon as possible, especially given how contagious each new variant is.

One gripe. I’m a bit miffed about the pace of things. It’s clear that, until today, Moderna had not submitted any official documents to the FDA, despite announcing favorable results from their pediatric trial over a month ago. Everything I have heard is that this reflects administrative incompetence over at Moderna rather than any scientific problems that they had to work out. I suppose that’s the preferable explanation, given the options. But given that we are now two years into this, and Moderna was able to produce its prototype vaccine in a matter of weeks back in 2020, it’s bewildering to me that this company would not have already had all of its documentation and paperwork ready to go before the data collection was complete, and simply filled in the blanks when the results came through. It’s a pandemic, people! We don’t have time for administrative slowdowns. Moderna’s stock is now 6-times more valuable than it was before the pandemic. You’d think they’d throw a few bucks at this.

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Bottom line: My family continues to be fairly cautious. We accept some risks, but we pick our battles. Our child goes to a pre-school where they do weekly (and sometimes twice-weekly) testing, and use masks indoors (though, thankfully, not outdoors, as this is probably pointless). We’ve done a little bit of travel to see family. But I’ve turned down most work-related travel, and we don’t go to indoor restaurants or other large indoor events we might normally attend. When we gather with friends indoors, we all do rapid tests right before. Having a fully vaccinated household will affect our choices (the caveat being we’re expecting a daughter in June, but I’ll say more on that another time); we will liberalize and take more risks—which is something I’m looking forward to.

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