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Effectiveness of using bivalent Pfizer booster vaccine in neutralizing SARS-CoV-2 in the elderly

Reviewed by Dat Tien Nguyen, B.A, ScM. 
Posted on Februaary 6th, 2023
As more people are immunized against SARS-CoV-2, and the virus mutated to be less lethal, COVID-19 has transformed from a pandemic to an endemic, like influenza. Despite this shift, it is still important to maintain high vaccination rates to reduce the risk of mutation that can generate new variants and to protect members of vulnerable groups such as the elders. The two pharmaceutical companies, Pfizer and BioNTech - the manufacturers of the BNT162b2 vaccine - had recently released their finding on the effectiveness of a bivalent vaccine vs. the current vaccine in neutralizing SARS-CoV-2.

The study included 1846 participants who were older than the age of 55, and had previously received three 30-μg doses of the BNT162b2 vaccine. These individuals were selected to receive six different doses and formulate of the BNT162b2 vaccine: 
  1. 30 μg of BNT162b2
  2. 60 μg of BNT162b2
  3. 30 μg of monovalent B.1.1.529 (omicron) BA.1– adapted BNT162b2 (monovalent BA.1)
  4. 60 μg of monovalent B.1.1.529 (omicron) BA.1– adapted BNT162b2 (monovalent BA.1)
  5. 30 μg of bivalent (15 μg of BNT162b2+15 μg of monovalent BA.1)
  6. 60 μg of bivalent (30 μg of BNT162b2+30 μg of monovalent BA.1)
The trial participants were asked to attend a follow-up meeting scheduled to be 1 month from the injection. The researchers found that both the 30 μg and 60 μg dose of the bivalent formulation was superior to the original BNT162b2 in terms of eliciting an immune response that can neutralize the BA.1 (Omicron) variant. Both formulations were equally effective at neutralizing ancestral SARS-CoV-2 strains. However, the bivalent formulation was overwhelmingly superior to the original Pfizer vaccine formulation in eliciting an immune response that can neutralize the BA.2.75, BA.4, and BA.5 subvariant of the Omicron variant. Since the Omicron BA.5 is the predominant subvariant worldwide, booster shot with the bivalent formulation can be useful in protecting the elderly from COVID-19. However, this study’s follow-up period of 1 month is too short to monitor for any long-term side effects. Additional study should also compare the clinical efficacy besides that serological effectiveness.