The objective of this opinion is to present an analysis of the risk of myocarditis / pericarditis linked to the vaccination of young people aged 12 to 39 years with mRNA vaccines, especially with regard to the administration of a second dose. This analysis was performed on an individual basis based on information available as of July 15, 2021. Vaccination strategies are being assessed in the context of the threat of a new wave of COVD-19 caused by the Delta variant. Provisional recommendations are issued from both an individual and a population perspective.
In view of the data currently available and all the uncertainties concerning the risks and benefits associated with the use of the two mRNA vaccines, the CIQ recommends offering two doses of these vaccines to all eligible young people aged 12 years. and more. In young people aged 12 to 17, only the vaccine from Pfizer-BioNTech has been used so far since it is the only vaccine authorized for this population. In addition, it is possible that this vaccine is associated with a lower frequency of myocarditis / pericarditis than that of Moderna. The CIQ therefore recommends continuing only with the Pfizer-BioNTech vaccine for the remainder of the vaccination campaign among young people aged 12 to 17. The vaccines from Pfizer-BioNTech and Moderna can be used for people 18 years of age and older. The contraindications, precautions and other specificities related to the use of mRNA vaccines are presented in a separate opinion.
The two mRNA vaccines are the most effective in preventing COVID-19 caused by all viral lines and transmission of the virus in the population. Any preferential recommendation of one of the 2 vaccines over the other could have very negative consequences in terms of the perception of their safety and their undeniable advantages and this could influence the already sub-optimal vaccine coverage among young people.
In the 18 to 39 age group, the 2 mRNA vaccines were used for the first dose, but more the product from Pfizer-BioNtech than that from Moderna. Although it is possible in certain circumstances to offer a different product for a second dose than that used for the first, the use of the same product for the 2 doses of messenger RNA vaccine is always preferable in the absence of evidence. on the safety, immunogenicity and efficacy of a mixed schedule combining the 2 mRNA vaccines.
Young people vaccinated, and possibly their parents, should be informed of the advantages and disadvantages of vaccination including the possibility of developing myocarditis or pericarditis in the days following vaccination, the higher frequency of this manifestation in young men after the 2e dose, and the importance of seeking medical attention in the event of dyspnea, chest pain or palpitations following vaccination. It is important for young people to be aware of the risks of myocarditis which may occur after the 2e dose of vaccine. At the same time, it is necessary to present the probability of avoiding infection or hospitalization due to COVID-19 thanks to this 2e dose, which appears particularly important in the context of the apprehended rise of the Delta variant, as well as the other benefits of vaccination for the young person and those around him. Tables 1A and 1B of this opinion could be used for this purpose.
This opinion is preliminary and is based on the still incomplete information concerning the signal of myocarditis and pericarditis in young people after the administration of mRNA vaccines. An update will be produced as needed according to the evolution of knowledge on this signal, the effectiveness of these mRNA vaccines including the effectiveness against the various variants, the evolution of the epidemiological situation of COVID-19 in Quebec from same as other program considerations that may influence the relevant immunization strategy for young people.