Ontario Immunization Advisory Committee recommended that if an 11 and 12-year-old child is inadvertently given a second dose of the Pfizer-BioNTech vaccine that is not authorized for their age, the dose should be considered valid and the series complete.
National Advisory Committee on Immunization (NACI) recommends that a booster dose of an authorized mRNA COVID-19 vaccine should be offered to vulnerable population and > 50 years old, =6 months after completion of a primary COVID-19 vaccine series.
Australian Technical Advisory Group on Immunization (ATAGI) recommends COVID-19 booster vaccination with either Pfizer (Comirnaty) or Moderna (Spikevax), which are considered equally acceptable, for anyone aged 18 and older who completed their primary course of COVID-19 vaccination 5 or more months ago.
On December 8th, 2021 in a press release by Pfizer-BioNTech said that preliminary laboratory studies demonstrate that three doses of the Pfizer-BioNTech COVID-19 vaccine neutralize the Omicron variant while two doses show significantly reduced neutralization titers. Data indicate that a third dose of BNT162b2 increases the neutralizing antibody titers by 25-fold compared to two doses.
Key Findings
December 3, 2021
The Therapeutic Goods Administration (TGA) has granted provisional approval to Moderna for the use of its vaccine in children (two 10µg doses) and as booster shot for adults (one 30µg dose) in preparation for the recent emergence of the Omicron variant. This is in addition to Pfizer, which was also recently approved.
The National Advisory Committee on Immunization (NACI) recommends that a complete series with the Pfizer-BioNTech COVID-19 vaccine (10 mcg) may be offered to children 5-11 years of age who do not have contraindications to the vaccine, with a dosing interval of at least 8 weeks between the first and second dose.
NNACI also recommends that children aged 5-11 years with a history of previous SARS-CoV-2 infection should be considered no longer infectious and symptoms of an acute illness should be completely resolved prior to vaccination.
Health Canada has authorized Moderna's COVID-19 vaccine (also known as Spikevax) to be used as a booster shot, using a half-dose of the vaccine.
The group designated in Saskatchewan as Clinically Extremely Vulnerable (CEV) is a heterogenous clinical population with factors that impair their immune response to differing degrees.
Very Limited evidence is currently available to assess the immune response following vaccination is selected clinical populations; no evidence is available to assess vaccine efficacy or effectiveness in these populations. The clinical relevance of measured immune response with respect to protection from disease is still uncertain.
In considering the immune response of the CEV population, it is recommended that the absolute difference in immune response between 1 and 2 doses be considered, as it is possible some patient groups will have lowered protection regardless of vaccine strategy.
In terms of clinical subgroups:
oOrgan transplantation recipients on immunosuppressive medication: solid organ transplant recipients receiving anti-metabolite maintenance immunosuppression therapy were less likely to develop an antibody response to an mRNA vaccine, compared to those receiving other types of therapies (37% vs 63%). In a study of 242 kidney transplant recipients on immunosuppressive therapy only 10.8% became seropositive at 28 days after a single dose of mRNA vaccine.
oCancer: A study of 151 elderly patients with solid and hematological malignancies and 54 healthy controls who received one or two doses of BNT162b2 (Pfizer-BioNTech) vaccine shows approximately 39% of solid cancer patients, 13% of hematological cancer patients, and 97% of healthy controls (p<0.0001) developed anti-S IgG 21 days following a single dose vaccine. However, response in solid cancer patients increased to 95% within 2 weeks of the second dose at 21 days.
oOther immunocompromising conditions (e.g., auto-immune disorders and therapy): some level of immunity is generated with vaccination; however, what this means clinically is unknown. It seems that ensuring the dosing is properly timed around biologic therapy is important.
Azizian, A; Lee, S; Shumilak, G; Groot, G; Reeder, B; Miller, L; Howell-Spooner, B. What are the risks or benefits of extended intervals between doses of COVID-19 vaccines compared to recommended dosing in extremely vulnerable populations? 2021 Apr 20, Document no.: EOC210302 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2021. 15 p. (CEST rapid review report).
Miller, L; Howell-Spooner, B. What are the risks or benefits of extended intervals between doses of COVID-19 vaccines compared to recommended dosing in extremely vulnerable populations? 2021 Apr 01; Document no.: EOC210302 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 22 p. (CEST evidence search report).
