Archived 10: National Advisory Committee on Immunization (NACI): Summary of extended dose interval statement of April 7, 2021

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This is an archived version. Please refer to the most current version of the recommendations on the use of COVID-19 vaccines.

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Overview of the statement

In the context of the ongoing pandemic, NACI recommends extending the time between the first and second dose of COVID-19 vaccines up to four months while vaccine supply is limited. Second doses should be offered as soon as possible after all eligible populations have been offered first doses, with priority given to those at highest risk of severe illness and death from COVID-19 disease. With Canada’s expected vaccine supply, the interval between the first and second dose is expected to be less than four months. Jurisdictions may choose to shorten the time between the first and second dose in specific populations based on local rates of cases and what is known about where transmission is happening, local vaccine supply, their local methods of delivering vaccine and emerging evidence.

Extending COVID-19 vaccine dose intervals will optimize vaccine rollout and protection of the population by allowing many more people to gain protection against COVID-19 by receiving the first dose of a COVID-19 vaccine earlier. This helps to provide direct protection to the individual and those around them and may also help to prevent spread in the community.

In making its recommendations, NACI carefully considered all available evidence about how well the COVID-19 vaccines work, as well as mathematical modelling, vaccine supply and public health principles of equity, feasibility and acceptability. Current real-world evidence indicate good vaccine effectiveness against symptomatic disease and asymptomatic infection and very good effectiveness against hospitalization after the first dose of COVID-19 vaccines.

NACI recommends that at this time it is very important to continue to follow public health measures as recommended by public health officials, regardless of vaccination status.

NACI will continue to monitor the evolving evidence and update its recommendations as needed.

NACI provides advice that is used by provinces and territories who are responsible for designing their immunization programs.

To see the full update, please visit Extended dose intervals for COVID-19 vaccine to optimize early vaccine rollout and population protection in Canada in the context of limited vaccine supply.

Background

On March 3, 2021, NACI released a rapid response statement recommending jurisdictions extend the time between the first and second dose of COVID-19 vaccines up to four months in order to provide good protection against symptomatic COVID-19 disease to more people faster.

Given the evidence that this strategy would have an important impact on reducing deaths and hospitalisations, NACI communicated their recommendations as fast as possible for jurisdictions to consider through a rapid response statement while the full report was being prepared.

NACI is now releasing the full advisory committee statement, which further explains the rationale behind this extended dose interval recommendation and includes references and detailed summaries of evidence updated to reflect the most recent data.  

Current evidence demonstrates very good vaccine efficacy (protection shown in clinical trials) and good vaccine effectiveness (protection in real-world use) against SARS-CoV-2 infection when the first dose of COVID-19 vaccine begins to take effect. Real world evidence of protection comes from Canadian and international jurisdictions that have implemented extended dose strategies, where this is being closely monitored, and from other countries who monitored the response from the first dose of mRNA vaccines before the second dose is given.

NACI continues to recommend that an extended interval of up to four months to rapidly provide vaccine to as many people as possible based on:

More information will become available as vaccination programs continue to roll out around the world. NACI will continue to closely monitor the evolving evidence on the effectiveness of an extended dose interval and will update their recommendation as needed.

It is important to remember that public health measures (e.g. washing hands, wearing a mask, staying 2 metres apart, avoid unnecessary interactions with others) are a key part of protecting yourself and the population; and people should not change their behaviours after the first or second dose of vaccine at this time.

To see the full update, please visit Extended dose intervals for COVID-19 vaccine to optimize early vaccine rollout and population protection in Canada in the context of limited vaccine supply.

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