I guess we all should be accustomed to the ups and downs of the pandemic. We continue to see good news with waning of the omicron surge around the world, but parents of children under 5 had a bit of a jolt on Friday with the news that the Pfizer vaccine will not be discussed by the FDA next week as originally planned. We now await ongoing data from the trial which has begun a booster dosing phase. Regular readers of Pediatric Infection Connection will know that I oversee this trial at Children's National Hospital, but I have no knowledge of the data submitted by Pfizer to the FDA so can't provide any independent opinion.
Booster News?
Speaking of boosters, CDC released some important new information about boosters, some of which pertains to children. First, an early release in MMWR highlighted waning of effectiveness of 2- and 3-dose mRNA vaccines. This is sort of a glass half empty or full view, I was actually more encouraged by the continuing effectiveness, particularly for boosted individuals, against severe disease and hospitalization. Just looking specifically at the data from the omicron-dominant time period, vaccine efficacy (VE) in preventing emergency or urgent care visits was 87% 2 months following a third or booster dose though dropped to 66% beyond 5 months (note few data available for this latter estimate). VE in preventing hospitalization was 91% and 78% for those 2 intervals post third dose. This is by no means the final word, lots of limitations in this study and also it looked only at individuals 18 years of age and older and did include a significant number of people with immunocompromise and other risk factors for severe COVID-19 disease. No information about how these risk factors specifically affected VE.
Also, as promised the CDC issued an update to guidance for vaccination of those with moderate or severe immunocompromise to include a fourth dose in some circumstances. This update applies to people down to 12 years of age and provides a good road map for vaccination of those individuals.
Variant Viewing
I'd definitely be happier stargazing or watching butterflies and bees in season, but lately I've been keeping an eye on the BA.2 subvariant of omicron. It has started to appear in our CDC data (after clicking on this link, choose Variants and Genomic Surveillance, then Variant Proportions from the left-side menu). BA.2 now comprises 3.6% of isolates as of Feb 5 compared to 96.4% omicron BA.1) and similarly has increased slightly in the UK. As I indicated last week, it is more transmissible than the original omicron variant, but it isn't clear whether prior infection with omicron BA.1 confers some immunity against BA.2. That is probably the key factor in determining if we will see another surge due to BA.2.
I also note some encouraging news in the UK that the reproductive number is now estimated at 0.8 to 1.0, a milestone that signals flattening or decrease in the pandemic. Of course it could be just another ride on the roller coaster but I choose to take this as a further good sign.