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Originally Posted by ford71V8

I was under the impression that while 3-6 week gap for Pfizer shots is correct, the efficacy is better at 6 than 3.
And any time longer than 6 is pointless.

The WHO advises that full protection requires two doses which WHO recommends be administered with a 21 to 28-day interval.

This Yale Medicine article states two shots, 21 days apart.

Interesting details in the Yale document (updated September 17, so pretty current) regarding efficacy and the need for a booster shot with the Pfizer (also known under the names of Pfizer-BioNTech, BNT162b2 or Comirnaty):

How well it works: Experts continue to learn about Pfizer’s efficacy both in the laboratory and in the real world. Pfizer’s initial Phase 3 clinical data presented in December showed its vaccine to have 95% efficacy.

In April, the company announced the vaccine had 91.3% efficacy against COVID-19, based on measuring how well it prevented symptomatic COVID-19 infection seven days through up to six months after the second dose. It also found it to be 100% effective in preventing severe disease as defined by the CDC, and 95.3% effective in preventing severe disease as defined by the FDA. Another study, not yet peer-reviewed, provided more new data that brought the efficacy number down to 84% after 6 months, although efficacy against severe disease was 97%.

In August, the CDC also published studies that showed mRNA vaccine protection against infection may be waning, although the vaccines were still highly effective against hospitalization. In one CDC study, data from the state of New York showed vaccine effectiveness dropping from 91.7 to 79.8% against infection.

I also note the following in the WHO article:

Does it prevent infection and transmission?
There is currently no substantive data are available related to impact of Pfizer BioNTech vaccine on transmission or viral shedding.

In the meantime, we must maintain and strengthen public health measures that work: masking, physical distancing, handwashing, respiratory and cough hygiene, avoiding crowds, and ensuring good ventilation