2-month cycle, children and immunity

As we enter a second Autumn with Covid still with us, we need to keep learning. Here’s what’s new this week.

1.?What is the 2-month Covid cycle? An article in the New York Times this week examines a peculiar cycle with Covid replicated in many countries around the world: the virus peaks over two months or so, and then begins to rapidly decline. In the U.S., the current Delta surge started in late June and peaked last week replicating a pattern seen with earlier strains of the virus. In India, last winter, Delta cases rocketed up for 2 months before peaking out and declining. In England, cases rose quickly to a peak after two months in July. In France, Spain, Thailand and Indonesia, the spike in cases also lasted around 2 months. Case numbers in Florida, Mississippi, Arkansas and Louisiana?peaked in early or mid-August?and have been falling. Epidemiologists speculate that the virus runs fast through a vulnerable population causing a peak, and then runs out of people to infect. The other explanation that may contribute to this 2-month cycle phenomenon is that people move around in response to external triggers such as Holidays or other events causing transient opportunities for the virus. The opening of schools around the country may offer again a new opportunity for the virus to take hold in a large cohort of unvaccinated children. There are also exceptions to this 2-month pattern. For example, Brazil which has suffered one of the worst outbreaks in the world has not shown the rapid decline from a peak. The cycle can also be shorter in places that have achieved high vaccination rates such as in Singapore and Malta where the virus surge cycle only lasted 2 weeks rather than 2 months. Widespread vaccination remains the best strategy to prevent new deadly Covid cycles.

?2.?What’s happening with childhood vaccines? This topic takes on more relevance as schools reopen and more parents feel compelled to send their children to in-person school rather than face another year of school on Zoom. Vaccine makers are still in the process of collecting data from children. Pfizer is hoping to file their data with the FDA later this month and ask for an emergency use authorization (EUA) as early as October. The FDA then needs at least several weeks to review the data. The earliest likely childhood vaccine might be ready by Thanksgiving. The Moderna trial in children is several months behind Pfizer and Johnson & Johnson has not even started yet. Part of the delay is that the FDA asked for 6 months of safety data for the 5–11-year-olds as compared with only 2 months that were required for adults.

?3.?CDC says 80% have some immunity. New data released by the CDC suggests that over 80% of Americans over the age of 16 have some degree of immunity from either Covid infection, immunization, or both. 1.4 million blood samples were tested in all 50 states and Puerto Rico. The data suggests that the majority of persons with immunity have this from vaccination rather than prior infection. Get vaccinated!