Archived 20: Summary of National Advisory Committee on Immunization (NACI) rapid response: Booster dose of COVID-19 vaccine in long-term care residents and seniors living in other congregate settings

Publication date: September 28, 2021

On this page

• Overview
• What you need to know
• Quotes

Overview

• On September 28, 2021, the Public Health Agency of Canada (PHAC) released updated advice from the National Advisory Committee on Immunization (NACI) regarding a booster dose of a COVID-19 vaccine for residents of long-term care homes and seniors living in other congregate settings. These recommendations are based on current scientific evidence and NACI's expert opinion.
• NACI has determined that there is an immediate need to provide a recommendation for a booster dose of a COVID-19 vaccine in residents of long-term care and seniors living in other congregate settings as they are at increased risk of infection and severe disease and due to signs that protection might not persist as long in these individuals as in other populations in Canada.
• In making this recommendation, NACI reviewed the available evidence on vaccine effectiveness and waning antibody responses of a primary series; the available evidence on the safety of and immune responses produced by a COVID-19 booster dose; Canada’s current COVID-19 epidemiology; and ethical and equity considerations.

NACI recommends that:

 To see the full update, please visit NACI rapid response: Booster dose of COVID-19 vaccine in long-term care residents and seniors living in other congregate settings.

What you need to know

• Seniors living in congregate settings are at increased risk of exposure to SARS-CoV-2 because of their daily interactions with other residents and staff. Seniors living in congregate settings are also at increased risk of severe COVID-19 outcomes due to their advanced age and underlying medical conditions.
• Due to these increased risks, residents of congregate living settings that provide care for seniors (i.e., long-term care homes, assisted living, retirement homes, and chronic care hospitals) were prioritized for vaccination during the initial rollout of COVID-19 vaccines in December 2020. Many residents received an mRNA vaccine series using the manufacturer-specified intervals (21 days between the first and second dose for Pfizer-BioNTech Comirnaty and 28 days for Moderna Spikevax).
• Evidence to date suggests that, compared to longer intervals, shorter intervals between the first and second dose in a primary series result in a lower immune response and more rapid waning of protection, including against variants of concern, is expected.
• In making this recommendation, NACI reviewed the available evidence on vaccine effectiveness and waning antibody responses of primary series, available evidence on the safety of and immune responses produced by a booster dose, and current COVID-19 epidemiology.
• NACI also considered an ethical analysis of recommending an off-label booster dose to long-term care residents and seniors living in other congregate settings completed by the PHAC Public Health Ethics Consultative Group (PHECG).
• Evidence from Canadian-led studies suggests that residents of long-term care produce a strong initial antibody response to a primary mRNA vaccine series (i.e., two doses). However, studies also suggest the majority of residents did not have a detectable level of antibodies against the Delta variant six months following the primary series.
• While there are limited data of waning vaccine effectiveness in residents of long-term care, there is a growing body of evidence showing waning vaccine effectiveness in countries that followed the manufacturer-recommended intervals for mRNA vaccines. Fortunately, evidence suggests that protection against severe outcomes appears to last longer than protection against infection.
• There are several studies underway looking at mRNA booster doses. Early results are showing a favorable safety profile and evidence of an improved immune response, although data specific to residents of long-term care facilities are limited. Two studies from Israel demonstrate the effectiveness of a booster dose in preventing SARS-CoV-2 infection.
• Long-term care homes in some areas of Canada have recently experienced an increase in COVID-19 outbreaks. This may be due to unvaccinated residents, staff and/or visitors; waning protection in residents; and/or the recent onset of the fourth wave of the pandemic driven by the Delta variant.

Due to the above considerations, NACI recommends that:

• Residents of long-term care and seniors living in other congregate settings who have received a primary COVID-19 vaccine series should be offered a booster dose of an authorized mRNA COVID-19 vaccine at a recommended interval of at least 6 months after the primary series. A booster dose of an authorized viral vector vaccine should only be considered when an mRNA COVID-19 vaccine is contraindicated or inaccessible.
• Informed consent should include discussion about what is known and unknown about the risks and benefits of providing a booster dose, including the off-label status of NACI's recommendation.
• In addition to residents of congregate living settings, it is very important that healthcare workers, staff, visitors, and other close contacts of residents receive a primary COVID-19 vaccine series in order to prevent them from introducing the virus into the congregate living setting, infecting the residents and causing an outbreak.
• NACI will continue to monitor the evolving evidence on the need for and effectiveness of booster doses in other key populations and the general population and will update guidance as needed.

To see the full update, please visit NACI rapid response: Booster dose of COVID-19 vaccine in long-term care residents and seniors living in other congregate settings.

Quotes

“Early in the vaccine rollout, residents of long-term care were prioritized for first doses of COVID-19 vaccines as a vulnerable population at risk of severe disease and death.  Now, as we move through a fourth wave of Delta variant, NACI has determined that there is an immediate need to provide a recommendation for a booster dose of COVID-19 vaccine to all long-term care residents and seniors living in other congregate settings, where evidence is emerging that protection might not persist as long as other populations in Canada.  The combined factors of high risk of exposure, high risk of severe outcomes, a relatively long time since receipt of their last dose, a short interval between doses, the impacts of facility outbreaks, and older age create conditions that could exacerbate the effects and consequences of waning vaccine protection against severe outcomes in this group.” 

“While the vaccines initially worked very well to protect this group, we are starting to see signs of outbreaks again in long-term care settings and we are looking to prevent the level of severe outcomes this population experienced early in the pandemic.  Providing a booster dose through a precautionary approach is expected to improve their protection. NACI is closely monitoring how well vaccines are performing in other key populations in order to determine if or when booster doses might be appropriate for other groups.  This advice is specific to residents of long-term care and seniors living in other congregate settings given the unique high risks they experience and does not mean that booster doses are necessary for the general population.”

- Dr. Shelley Deeks, NACI Chair

“We welcome this advice from NACI, which will help us protect individuals in long-term care, who were among the hardest hit during the earlier stages of the pandemic due to their increased risk of infection and severe outcomes from COVID-19. At this time, boosters are not necessary for most of the population, but we want to be sure to address early signs of waning among seniors residing in these settings where shared and close living spaces increase the risk of exposure. Boosting immunity levels in seniors living in long-term care settings will help to maintain their protection against infection and serious illness.”

- Dr. Theresa Tam, Chief Public Health Officer