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.
Low grade evidence shows IgG and IgM antibody response correlates with neutralizingantibody titerand viral clearance, which is suggestive of protective humoral immunity inCOVID-19 patients with mild to moderate symptoms.
There is no available evidence with which to estimate the durability of this protective response. However, if the immune response to SARS-CoV-2 resembles that toward SARS-CoV, this protective humoral immunity may persist for several years.
Higher IgG antibody titersand a robustresponse were noted in severe to criticallyill patients and were associated with lower viral clearance and a worse clinical prognosis.
Low grade evidence suggests that convalescent plasma treatment may improve the clinical status of critically ill COVID-19 patients(one case series with only five patients enrolled).
Miller, L, Howell-Spooner, B. What is known about safety/efficacy of global vaccines not approved in Canada? What are the impacts on international travel and vaccination policies? 2021 Jul 16, Document no.: INF210701 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2021. 24 p. (CEST evidence search report).
Young, C; Howell-Spooner, B. What is the duration of immunity for COVID-19 in previously infected patients? 2020 Dec 29; Document no.: INF090101v3-01 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 39 p. (CEST evidence search report)
· First confirmed case of reinfection documented in a 33 year-old man in Hong Kong, who was first infected with the virus in March, and again while on holiday in Spain four and a half months later – though asymptomatic for both infections
· Genetic sequencing has identified a small number of reinfection cases with different strains
· No concrete evidence on the presence and/or duration of immunity to SARS-CoV-2 in humans
· Demonstration of PCR positivity does not necessarily indicate continued or renewed infection; it may indicate the presence of a dead virus.
· In-vitro analyses have documented the presence of SARS-CoV-2 antibodies in convalescent samples up to eight months post infection
· Only one small study in rhesus monkeys recovered from SARS-CoV-2 were not re-infected when re-challenged with SARS-CoV-2 upon recovery
· Many cases series of previously recovered SARS-CoV-2 patients re-testing positive following clinical and pathological recovery, but virus has been unable to be cultured from those patients, most remain asymptomatic and there have been no documented secondary cases arising from patients following positive re-tests
Badea, A; Lee, S; Groot, G; Takaya, S; Dalidowicz, M; Howell-Spooner, B. What is the duration of immunity for COVID-19 in previously infected patients? 2021 Jan 20; Document no.: INF090101v2 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2021. 26 p. (CEST rapid review report)
Dalidowicz, M. What is the risk of reinfection from COVID-19? 2020 Mar 24; Document no.: EOC032401-01 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 3 p. (CEST evidence search report)
Badea, A; Lee, S; Shumilak, G; Dalidowicz, M. What is the risk of reinfection from COVID-19? 2020 Nov 2; Document no.: EOC032401v3 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 13 p. (CEST rapid review report)
