Let's talk about pediatric vaccines. Not COVID-19 yet (soon, @synapse2000 !), as I am waiting to hear back from some folks in the know, but a pediatric vaccination 101 for context. It's a rabbit hole. My context is being a board-certified pediatrician who has worked ...

... in both the US and Canada, and trained under Tom Saari, who chaired the Red Book Committee some time back. Of course, nobody knows exactly when we'll get the first doses in kids, but the context will help interpret opinions.

First, kids are not just small adults. Their bodies work differently. Interestingly, although there are a few differences between adults and kids re: vaccines, the primary one is that sometimes kids need *higher* doses. So, for example, the kid tetanus vax (DTaP) has roughly ...

... twice the antigen load as the adult Tdap. So if you use the adult dose on a kid, they are undervaccinated. But when the reverse has happened, there is primarily just an increased risk of local site reactions. (I will dig up the links at the end of this, but there is case ...

... series reports in the literature). This means that sometimes the dose between adults and kids is the same, and sometimes kids need more. While there are still priority adults to vaccinate, it's unlikely we will vaccinate kids without more data. Can't waste doses.

And sometimes kids need more doses. For example, the influenza vaccine in Canada is first given to kids between 6mo and 9y as two doses spaced at least 4 weeks apart. This is not a "split dose" -- the increment is 0.5ml, regardless of age (w/one exception, IIV3-Adj, because ...

of the type of vaccine comes as 0.25ml aliquots). In the US, the influenza vaccine is given to kids on a similar schedule, but some brands of vaccine call for a 0.25ml aliquot, and some for 0.5ml. Regardless, it is not a "split dose" -- it's two doses the first season given.

So I think the primary challenge to pediatric COVID-19 vaccination is knowing whether we will undervaccinate them by using the adult dose. Maybe, maybe not -- but we need data. So how about side effects?

There are some side effects specific to age, but they aren't really about the child's immune system. HPV vaccination (Gardasil, and others) in young teenage girls was noted to have an association with fainting -- but the same is true for all "shots" in that age group. They ...

... have a lower blood pressure in general (not uncommon to see 90s over 60s), and they are more likely to have orthostatic hypotension symptoms. Another more common adverse response in kids is development of DTaP granulomas, or hard knots in the tissue of injection.

But this is likely just a localized inflammatory reaction in the tissue, and recall that about double the provocation is given in the peds dose. IIRC, there were some granulomas when the pediatric dose was given to adults.