, “Pfizer reported vaccine efficacy of 52 per cent from Day 1 after dose 1 to before dose 2. This is an important reminder that it takes time for the full immune response to be mounted. Therefore, the risk of acquiring COVID-19 does not drop immediately after vaccination with the first dose.… The interval between the first and second doses was not studied for long periods in most clinical trials and thus the optimal interval between doses remains unknown.
The United Kingdom is pulling the same stunt as Canada because of supply issues. In response, Stephen Evans, a professor of medical statistics at the London School of Hygiene & Tropical Medicine and a former drug-safety committee member at the European Medicines Agency,, “The data for how well the vaccines work after one dose isn’t clear cut. Pfizer’s shot was 52.4 per cent effective between doses after 11 days and could be between 29.5 per cent and 84.5 per cent according to FDA documents.