Name: Comirnaty™  (BNT162b2)

Type: Genetic vaccine (messenger RNA/mRNA)

Developer: Pfizer/BioNTech

Recommended schedule: 2 doses (3-6 weeks apart)

Doses for Australia: Contract for 40 million doses to be delivered in 2021

Manufacturing: Doses for Australia will be manufactured overseas

Storage: Must be stored at ultra-cold temperatures of -90°C to -60°C. Unopened vials can be stored and transported at domestic freezer temperatures (-25°C to -15°C) for up to 2 weeks. Vials held at these temperatures can then be returned to ultra-cold temperatures for longer term storage ensuring that they remain within the manufacturer’s use by date. Unopened vials can be stored for up to one month (31 days) at temperatures of 2°C to 8°C. Once thawed, Comirnaty™ cannot be refrozen.

Preparation and injection: The vaccine must be thawed before preparation and should only be diluted with the recommended diluent. After reconstitution the vial must be used within six hours.  Each multi-dose vial (MDV) contains 5 doses of 0.3ml to be administered via intramuscular (IM) injection.

Background

Comirnaty™ uses a messenger RNA (mRNA)  platform which codes for the SARS-CoV-2 full-length spike protein. On 25 January 2021, Comirnaty™ was the first COVID-19 vaccine to be granted provisional registration in Australia for people aged ≥ 16 years. Eligibility has since been expanded to include individuals aged ≥ 12 years.

Immunogenecity

Pre-clinical trials were conducted in non-human primates (rhesus macaques) and mice. Vaccinated primates, who were challenged with SARS-CoV-2 virus, had no virus detected in the lower respiratory tract and clearance of virus in the nose within three days. These results indicated the vaccine may reduce both infection and transmission.

The US Phase 1 trial included participants aged 18 – 85 years old and compared a placebo to one of two vaccine candidates (BNT162b1, which encoded the SARS-CoV-2 receptor-binding domain; or BNT162b2, which encodes the SARS-CoV-2 full-length spike protein). This trial supported the selection of BNT162b2 (full length spike protein) for advancement to Phase 2/3 trials.

Two doses of BNT162b2 were shown to elicit high SARS-CoV-2 neutralising antibody titres and robust spike protein-specific T-cell responses.

Safety profile

During clinical trials, symptoms following immunisation with Comirnaty™ were generally mild to moderate and generally short-term. They were less common and milder in older adults (>55 years), compared to younger adults (<55 years). Local reactions including pain (66-83%) and redness (5-7%) at the injection site were more common after the first dose compared to the second dose. Systemic reactions (including fatigue, headache, muscle ache and headache) were more common and severe following the second dose. The incidence of serious adverse events was low and similar in both the vaccine and placebo groups.

Vaccine efficacy

Phase 3 trial data showed 95% vaccine efficacy. Similar vaccine efficacy (generally 90 to 100%) was observed across all subgroups defined by age (>16 years), sex, race, ethnicity, baseline body-mass index, and the presence of co-existing conditions. Older adults, 65 years and over, also had the same vaccine efficacy as younger adults. An immune response was detected less than two weeks after the first dose, and a second dose three weeks later, boosted that response. The study was not designed to assess the efficacy of a single-dose regimen, however, in the interval between the first and second doses, the observed vaccine efficacy against COVID-19 was 52%, reaching full efficacy at least seven days after the second dose.

Further studies

Paediatric clinical trials

Children were not included in the initial Pfizer/BioNTech clinical trials due to the decrease in severity of symptoms experienced by children infected with SARS-CoV-2 compared with infected adults. Various clinical trials are currently underway to determine the safety and efficacy of Comirnaty™ in the paediatric population.

For further information refer to MVEC: COVID-19 vaccination in children.

Mixed vaccine schedules

Clinical trials are currently underway to evaluate the immunogenicity and reactogenicity of combining Comirnaty™ with different COVID-19 vaccine brands to complete a COVID-19 vaccine course.

For further information refer to MVEC: COVID-19 mixed vaccine schedules.

Post-licensure surveillance

Allergies

A true vaccine allergy (anaphylaxis) is a rare side effect occurring for all vaccines at a rate of approximately 1 case per million vaccine doses administered. Post-licensure surveillance of Comirnaty™ in the US has shown that it has a slightly higher rate of anaphylaxis with approximately 4.7 cases per million doses administered. Most cases (89%) occurred within 30 minutes of vaccination and 24% had a history of prior anaphylaxis.

Myocarditis/pericarditis

A small number of cases of myocarditis and pericarditis have been reported in individuals vaccinated with COVID-19 mRNA vaccines (eg. Comirnaty™ and Moderna). Reports have predominantly involved adolescents and young adults, more commonly males, after the second dose of vaccine. Symptom onset has typically been seen within 4 days of vaccination.

Resources

Authors: Daniela Say (MVEC Immunisation Fellow) and Nigel Crawford (Director SAEFVIC, Murdoch Children’s Research Institute)

Reviewed by: Rachael McGuire, (MVEC Education Nurse Coordinator), Francesca Machingaifa (MVEC Education Nurse Coordinator) and Davina Buntsma (MVEC Immunisation Fellow)

Date: 3 August 2021

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.