OTTAWA -- The National Advisory Committee on Immunization (NACI) has updated its COVID-19 vaccine guidance again, now saying that second shots should be offered “as soon as possible.”

After recommending that second shots be delayed by up to four months, the updated position comes on the heels of several provinces already accelerating their timing of administering second doses.

“With the increase of COVID-19 vaccine supply in Canada, second doses should be offered as soon as possible, with priority given to those at highest risk of severe illness and death from COVID-19 disease after or concurrent with first doses for all remaining eligible populations,” said NACI in its latest release.

NACI said the interval of up to 16 weeks was “the upper limit” based on supply constraints and an effort to widely disperse some degree of protection with first doses, but now’s the time to start accelerating the timing of people’s second shots.

“Now that we are very quickly approaching the point where first doses are being offered to all eligible adults and adolescents, it is important that second doses start as soon as possible, particularly for those who are at highest risk of severe illness and death from COVID-19,” said NACI Chair Dr. Caroline Quach-Thanh in a statement on Friday.

NACI also said Friday that after reviewing additional evidence, safety information, and real-world data, it concluded that a full two-dose mRNA vaccine series should be what is offered to people who are immunosuppressed, have an autoimmune condition, are pregnant or are breastfeeding.

“Over time, we have seen very encouraging evidence for these vaccines in populations who were not included in the original clinical trials. Given the ongoing risks of COVID-19 exposure and severe disease in Canada, NACI is strongly recommending vaccine for these populations who are pregnant, with autoimmune, and immunosuppressive conditions along with the rest of the population,” said Quach-Thanh.

In terms of what to expect next from NACI, the arms-length panel says it is working on recommendations related to the interchangeability of mRNA and viral vector COVID-19 vaccines for release in early June.

As well, expected sometime this summer, the expert panel of medical professionals says it’ll have more to say on the “optimal number of doses” for people who have previously had COVID-19 and on the “co-administration” of COVID-19 with other vaccines.