The polemic second dose of the vaccine : There are fears that a single dose may not be as effective as the authorities have predicted

Doctors wrote to ministers expressing serious concerns about the timing of the coronavirus vaccine, warning that patients are at risk if they do not receive a second dose in a timely manner. 

In a letter sent to the secretary of health, the minister responsible for vaccines and the head of the SUSthe doctors criticised the lack of guidance surrounding the decision to change the period between doses of the Pfizer-Biontech vaccine from three weeks to 12 weeks.

Source: UK News