INSPQ INSPQ Public Health Expertise and Reference Center Study on healthcare workers: vaccination offers good protection against COVID-19

A study conducted by the Institut national de santé publique du Québec (INSPQ) among healthcare workers reveals a high rate of effectiveness of messenger RNA vaccines against infections caused by SARS-CoV-2. The Pfizer and Moderna vaccines, which were the subject of the analysis due to the fact that they were mainly offered to this population, are 70.9% effective in preventing any SARS-CoV-2 infection after a first dose and 86.9% after the second dose. For symptomatic infections, the efficacy is 73.4% after one dose and 94.2% after two doses. Finally, the effectiveness in preventing hospitalizations is 97.9% after the administration of a single dose of vaccine and 100% after two doses.

These data are reassuring for the immunization prospects of the general population and in particular for the protection of health care workers, who, by the nature of their work, constitute the group most exposed to the virus. The health workers who participated in the study are part of the staff paid by public or private health establishments under agreement. Participants do not include workers in clinics, pharmacies, private seniors' residences, etc., or physicians and medical residents.

Stable vaccine efficacy during the 16 weeks following the first dose

It is interesting to note that, overall, vaccine efficacy remained stable for the period ranging from 2 to 16 weeks following the injection of the first dose. This finding demonstrates that the decision of the Government of Quebec to delay the administration of the 2^th dose in order to provide some immunity to a larger proportion of the population has proven to be wise. .

Good vaccine efficacy against the Alpha variant

The emergence of worrying variants at the start of the year raised many questions about vaccine efficacy in the field. In Quebec, the Alpha variant that first appeared in the United Kingdom is the one that predominated during the period analyzed. The study shows good efficacy against this variant, which does not decrease over time, but is nevertheless 10% lower than against other strains of SARS-CoV-2.

Immunization status of healthcare workers

As of May 22, 2021, 81.9% of healthcare workers in public or private institutions under agreement had received at least one dose of the COVID-19 vaccine and 34.6% had received two doses. Note that vaccine efficacy is calculated from 14 days or more after a single dose of vaccine and 7 days or more after two doses, with an interval of at least 3 weeks between doses according to the manufacturers' instructions.