Efficacy Versus Effectiveness

I had doubts about the UK authorities deciding to change the dose regime for the Pfizer/BioNTech vaccine. They decided (as the vaccine was initially in short supply), to maximise the numbers of people getting first injections, by extending the time between the 2 doses from 3 weeks (as used in that vaccine's trials), to up to 12 weeks. Pfizer did not recommend this, apparently, somewhat arbitrary decision. Recent developments (e.g. studies showing that extending the time between the 2 injections, improves the effectiveness of both the Pfizer/BioNTech and Oxford/AstraZeneca vaccines) and an opinion piece by David Spiegelhalter and Anthony Masters (https://www.theguardian.com/theobserver/commentisfree/2021/feb/28/both-covid-jabs-are-working-well-in-the-real-world-not-just-the-lab ), have changed my views. Spiegelhalter and Masters point out that there is a difference between a vaccine's efficacy and its effectiveness. The former (needed for vaccine approval) uses a double blind technique (to avoid bias) with carefully balanced (in terms of age, gender, fitness and ethnicity) experimental (who get the vaccine) and control (who do not) groups. Effectiveness, on the other hand, looks at the treatment's performance in the 'messy' real world (with lots of variability between subjects and no attempt to hide who gets the vaccine). There now seems little doubt that the policy of giving as many first jabs as possible is driving down hospital admissions rates for people with a Covid-19 infection. And, as we say in English, 'the proof of the pudding is in the eating'. The only provisos that I would add are that a) protection after a first dose is not immediate and b) getting the second dose is still important, to help maximise the vaccine's effects. People need be reminded about these two facts, before rushing off to their former lives after receiving the first jab.