Abstract
- NACI has considered evidence from recent scientific studies on efficacy and effectiveness of COVID-19 vaccines in preventing various health outcomes such as infection, symptomatic disease, hospitalizations and death from COVID-19.
- While studies have not yet collected four months of data on vaccine effectiveness after the first dose, the first two months of real world effectiveness are showing sustained high levels of protection.
- Short term sustained protection is consistent with immunological principles and vaccine science where it is not expected to see rapid waning of a highly effective vaccine in adults over a relatively short period of time. Extending the interval between doses was shown to be a good strategy through modelling, even in scenarios considering a six month interval and in theoretical scenarios where waning protection was considered.
- NACI recommends that in the context of limited COVID-19 vaccine supply, jurisdictions should maximize the number of individuals benefiting from the first dose of vaccine by extending the interval for the second dose of vaccine to four months.
- Extending the dose interval to four months allows NACI to create opportunities for protection of the entire adult population within a short timeframe. This will not only achieve protection of the adult population, but will also contribute to health equity,
- NACI will continue to monitor the evidence on effectiveness of extended dose intervals and will adjust recommendations as needed.
- Recommendation
- Americas
- Canada
- dosing schedule
- COVID-19
