This is of course exactly what was expected, and why First Dose First was so clearly the right strategy until countries had plenty of supply. Good for the UK recognizing this early. The US hasn't.
I do agree with you on the whole, but for me it’s a very difficult choice, not an obvious one.
I guess my point is, I'm not an expert in this area but there was a lot of chatter earlier that this was kind of predictable or something.
The decisions made in UK and Canada to delay the second dose were not a random choice. They were expected to work based on the body of knowledge we have from other vaccines and what we know about the immune system. It was by no means a certainty, but a strong probability. And it paid off.
For children receiving their first vaccines for the flu (whether inactivated or live), it is recommended they receive two doses 4 weeks apart.
Lots of the early childhood vaccines have minimum spacings of 4 weeks, but are given at 2, 4, and 6 months simply because of standard pediatric followup visit schedules: DTaP, Hib, IPV, PCV13, and Rotavirus. HepB has a first dose at birth and the second at 4 weeks -- 2 months.
HPV is available in a 3-dose series with 4 weeks between the first two doses.
https://bexsero.ca/content/dam/cf-pharma/bexsero/en_CA/docum...
The human trials had already shown that just one dose of Pfizer has an efficacy of 89% after 15 days. With a fast-spreading pandemic, the priority is to get as many people on their first dose as possible. This both starts to reduce the rate of infection, and also reduces the death rate.
The long-term effectiveness isn't a priority at first for the most developed countries. If necessary they can just order more vaccine after a few months and run a booster campaign later in the year. Cost isn't an issue.
https://www.forbes.com/sites/carlieporterfield/2021/07/21/st...
> Two doses of the Pfizer vaccine had an effectiveness of 93.7% at preventing symptomatic alpha infections, and 88% for the delta variant.
[..]
> However, the effectiveness of the vaccines plummeted if a patient had only received one dose of either vaccine: the study found both to be just more than 48% effective against alpha and only about 30% effective against delta.
I'm a little confused as to what your point is? The vaccines are highly effective after two doses, but not very effective after only one dose.
Thank you for following up- I appreciate it.
That said, other studies are available, and some have shown decent performance against Delta after one dose.
There were enough volunteers for them.
This was not some random experiment on the population. While the gold standard of a phase three trial was not available to support the longer interval, there was plenty of data about the performance of prior vaccines, and interim data about immunogenicity with a longer interval for the COVID-19 vaccines.
The effects of a single dose were reasonably well understood as well as the impacts on transmission. Reducing transmission is a potentially more relevant goal than individual health outcomes in the grand scheme of things.
Our government decided against the emergency usage in the end, and it was the right decision in hindsight, as it turns out that the vaccine is far less effective than its competitors, and could very well have had similar problems as AZ or Biontech.