Where is the BA.2 Surge?

A period of disappointing vaccine data for kids

BA.2 is on the cusp of becoming the most common variant in the US, yet total cases continue to decline. The only other variants still remaining are the other two Omicron lineages, which have been outcompeted by BA.2. The uptick in American cases which I was expecting is nowhere to be seen so far. Surveying Europe, it now is clear that BA.2 caused secondary spikes prolonging the Omicron wave; and that in the UK, Belgium, Germany, Austria, France, Italy and other countries this wave began simultaneously around March 6th. Most of those locations have seen a peak and are declining now, which is good news for them and for us. So has the canary left the coal mine, and is our pandemic trajectory uncoupled from Europe this time around? I predicted differently, but with three weeks elapsed from the onset of the BA.2 wave in Europe I have to think the odds are increasing in our favor. A simple answer like warmer weather may be a factor, but then so may a few dozen others. Among the most obvious are vaccination and booster rates, relaxation of non-pharmacologic mitigation efforts, and the timing of the arrival of BA.2. If the BA.2 variant became dominant here later into the Omicron wave than it had in Europe it will be facing a greater amount of Omicron generated immunity, which is quite effective. We should have an answer pretty quickly; the passage of each week puts us further into the very lucky category, which would be a refreshing change.

The last several weeks have delivered important news regarding the efficacy of the RNA vaccines for young children. Admittedly you might hear a more sanguine interpretation of the data from the Pharma companies, the CDC and the mass media, but you decide for yourselves. Data from the New York Department of Health on an extremely large cohorts of 5-11 year olds and 12-17 year olds for the six week period from mid December to January 30th, showed a dramatic decline in Pfizer’s vaccine efficacy during the Omicron era. Vaccine ability to prevent infection in the 5-11 year olds fell from 68% to 12%, and for the last week of the period, when Omicron represented all the virus circulating, the efficacy fell to 11%. Vaccine did better in the older age group declining from 66% to 51% effectiveness. As far as protection against severe disease is concerned, the data from the preprint, published February 28th, shows that during the Omicron dominant final month, 144 vaccinated children were hospitalized in New York State, and 286 unvaccinated kids were hospitalized. Considering that only 40% of New Yorkers 5-11 are vaccinated those numbers don’t look good. The statistical analysis the Department of Health applied concludes that vaccine efficacy in preventing hospitalization fell from 100% in the Pre-Omicron era to 48% now, but the confidence intervals are so large as to suggest darts thrown at a target by a slightly inebriated monkey. So I prefer to look at the raw numbers I just gave you above. (Although not specifically stated it appears there were no deaths in the 5-11 year group.) Now there are a lot of children in this age group with significant co-morbidities for whom any respiratory infection, not just COVID, is an invitation to the hospital, the ICU or worse. Although not spelled out in the data released, it is a solid bet that the majority of hospitalized children had a readily identifiable co-morbidity. Bare with me now for just one simple calculation which I think is important as you inform your decisions around this. Among the 365,502 fully vaccinated kids, 144 were hospitalized during the month of purely Omicron surge, or .00039 = .039% = 4/100th of 1%. What about the unvaccinated children? Well the preprint doesn’t provide us with a denominator, so I will have to estimate based on the information that of 40% of New York kids in the age group are vaccinated. That would give us 548,253 unvaccinated children and 286/548,253 = .052% hospitalized during a month of Omicron. These are very small differences between rare events. So while the scientists reporting the data, and the media cheer-leaders may say, “Even though the vaccine failed to prevent infection, it was still 48% effective in preventing hospitalization”, you have to realize that a 48% reduction in something that happens frequently is consequential, a similar reduction in something that happens very rarely is a different ballgame when balancing risk and benefit.

Then there is the data Moderna submitted this week to the FDA, seeking approval for their vaccine in younger children. Very briefly their data from the controlled clinical trial showed vaccine efficacy of 44% in the 6 mo-2 yr old group, and 38% in the 2-5 yo group. There were no deaths or hospitalizations in either the vaccinated or control group so no estimate of efficacy in preventing severe disease is possible. If you are thinking these numbers look better than Pfizer, you’re correct. Let’s keep in mind however that this clinical trial was run starting in October when there was no Omicron around, and vaccines were much more effective against the prior variants. We can’t judge from the data released so far how much of that reported efficacy was against a Delta virus which no longer is circulating.

What are the arguments for vaccinating the 6 mo-5 yo age group? Well they have changed over time, like many of the moving targets during the pandemic. The argument that vaccination prevents infection is now severely weakened and for me, with the current data, basically off the table. We should vaccinate the very young so they don’t bring the virus home and infect grandma or grandpa, or any severely immunocompromised family or classmates. That falls by the wayside also when the vaccine fails to prevent infection in any significant percentage of children, and plenty of data shows that vaccinated breakthrough cases shed lots of transmissible virus. Unvaccinated children will be a reservoir of infection prolonging the pandemic. Well at this point we are all, vaccinated or not, a potential reservoir of infection as successive variants have significantly diverged from the original Wuhan strain upon which the vaccine was developed. Vaccination will protect against severe disease; we just went through the numbers involved above. Even if your healthy child is extremely unlikely to develop serious illness, you don’t want them to miss school. In this age group almost all illness is a mild, short term affair; missing school can be an inconvenience for the parents, but is that really what we want to base the decision on when we fully expect kids of this age group to contract numerous viral respiratory illnesses (which we don’t vaccinate for) and miss school quite a few times. Finally, an argument can be made that vaccination produces a better immune response to a wider spectrum of the variants we have seen so far than infection with Omicron. This is true, but at the current point in time Omicron variants are the only virus around. You could make the leap of faith that vaccination with the current Wuhan vaccine will provide good protection from the next variant to emerge, better than it does for Omicron, but that is a big leap. No one knows for certain whether or when a significant new variant with world wide distribution will occur. Similarly we have no clue whether that hypothetical variant will be more or less virulent than Omicron. Protecting our children is one of the most important, and in many cases anxiety provoking activities in life. I have frequently given advice in these pages on vaccination for adults, boosters and their timing, and recommendations for immune-compromised adults. I hope the information collected here is useful in making your own decision regarding vaccinating the very young.