The British Medical Association has warned of too long a delay between the injection of the first and the second dose of the Pfizer / BioNTech vaccine because, according to its experts, waiting too long could reduce its effectiveness .
In the United Kingdom and in Quebec, the strategy adopted by governments is to offer a first dose of the vaccine to a larger number of people, even if it means extending the deadline for the second injection to almost three months. More specifically, in mid-January, Quebec recommended injecting the second dose of the vaccine within 42 to 90 days.
However, the head of the British Medical Association, Dr Chaand Nagpaul, warned that this decision could have an impact on the effectiveness of the vaccine, and recommends instead that the time between the two doses be limited to six weeks, or half of the time currently allocated.
Citing a World Health Organization study that recommended delaying the injection of a second dose of Pfizer’s vaccine in exceptional cases, Dr Nagpaul explained in a letter to the British government cited by the BBC that the strategy was “difficult to justify”.
“Obviously the protection will not go away after six weeks, but what we don’t know is what level of protection will be offered,” he told the BBC Breakfast show on Sunday. , claiming to understand “compromise and reasoning, but if it was the right thing to do, we would see other nations follow suit.”
However, there is a difference between the vaccine developed by Pfizer / BioNTech and that of Oxford / AstraZeneca, developed in the United Kingdom. In the case of Pfizer’s vaccine, which is the most widely used in Canada, vaccine efficacy is based on administration of the second dose after only 21 days. It is therefore difficult to know, at this stage, how effective this vaccine remains after the 21-day period has passed, and whether it remains valid after 90 days.
Despite criticism from some specialists in Quebec and elsewhere, Quebec’s chief public health officer, Horacio Arruda, has defended the strategy a few times. “We must understand that we are in a pandemic and that there are people who are currently dying,” said the national director of public health, Horacio Arruda, at a press conference in early January. We believe that protecting as many people as possible in the short term will save lives significantly, “he continued, believing that a single dose” still gives fairly adequate protection. “
For now, the injection of the second dose for those already vaccinated is scheduled for March.