HALIFAX -- The National Advisory Committee on Immunization (NACI) has provided new recommendations on vaccine interchangeability saying that COVID-19 vaccines types should remain consistent.
鈥淣ACI recommends that the vaccine series be completed with the same COVID-19 vaccine product when possible. If the vaccine product used for a previously received dose is not known, or not available, attempts should be made to complete the vaccine series with a similar type of COVID-19 vaccine,鈥
For example, the committee says a vaccination series started with a mRNA vaccine should be completed with another mRNA vaccine and the series should not be restarted. By contrast, NACI said if a second dose of the Oxford-AstraZeneca vaccine is unavailable it could be supplemented with the single-dose Johnson & Johnson鈥檚 Janssen vaccine.
鈥淚n the event that an individual receives one dose of the AstraZeneca vaccine and is unable to receive the AstraZeneca vaccine for the second dose, one dose of Janssen vaccine (if available) can be used as the second dose to complete the vaccine series,鈥 the statement reads.
Currently, no data exist on the interchangeability of COVID-19 mRNA vaccines, according to the committee.
鈥淗owever, the spike proteins encoded by either of the authorized mRNA vaccines are stabilized in the same manner to remain in the pre-fusion conformation, though other vaccine components like the lipid nanoparticle and the mRNA sequence may be different,鈥 the statement reads.
The committee says there is no reason to believe that mRNA vaccine series completion with a different authorized mRNA vaccine product would result in any additional safety issues or deficiency in protection.
Currently, data only exist on the expected reactions of a mixed schedule with the AstraZeneca and Pfizer-BioNTech COVID-19 vaccines, according to the committee.
鈥淩ecommendations on which vaccine product to complete a vaccine series in individuals who have received one dose of the AstraZeneca COVID-19 vaccine will be forthcoming after further evidence on mixed COVID-19 vaccine schedules is available,鈥 according to the statement.
The data is expected to be released in June.
Several provinces have paused the rollout and administration of the first doses of the AstraZeneca vaccine, citing safety and supply concerns.
On Friday, Ontario public health officials announced they will offer the province鈥檚 remaining inventory of AstraZeneca COVID-19 vaccine to those awaiting their second dose of the shot, citing preliminary results from that show the risk of adverse effects is low enough to proceed.
The province will not offer AstraZeneca shots to anyone else as a first dose, except in very limited circumstances. Nova Scotia, New Brunswick, Quebec, Manitoba and Alberta have yet to announce whether a second dose of AstraZeneca will be offered.
