How effective are the Pfizer / BioNTech and AstraZeneca / Oxford COVID 19 vaccines likely to be with a longer period between the two doses, compared to those separated by 3 weeks?
Clinical trial data suggests that the Pfizer / BioNTech vaccine doses should be spaced out by 3 weeks i.e. dose one followed by dose two 3 weeks later. The AstraZeneca / Oxford vaccine has limited data suggesting that a longer period than 3 weeks between doses may be preferable.
No further trial information is available yet to give decisive answers on this.
Sadly there are very few vaccines for the treatment of bacterial infections and much more research is needed for this too.