No Surprise ,Pfizer and BioNTech said initial lab studies show a third dose of their Covid-19 vaccine may be needed to neutralize the omicron variant

the staff of the Ridgewood blog

Ridgewood NJ, having only been on the global radar since late November, early analysis around the world regarding the Omicron variant of concern (VOC) is providing insight into its characteristics and risks. Some preliminary laboratory analyses suggest that the Omicron variant could exhibit some resistance to SARS-CoV-2 vaccines. One study conducted by researchers in Germany (preprint) found that blood serum collected from fully vaccinated individuals had reduced efficacy in neutralizing the Omicron variant. The researchers tested sera from a variety of vaccinated patients, including those who received the Moderna, Pfizer-BioNTech, and AstraZeneca-Oxford vaccines, including some with heterologous combinations and some who received booster doses. The researchers observed reductions in neutralizing capacity on the order of 10-30 times, compared to the Delta variant. Additionally, sera from participants who received a heterologous combination of the AstraZeneca-Oxford and Pfizer-BioNTech vaccines exhibited “no efficacy against Omicron.” Preliminary findings from studies conducted by researchers in South Africa and Sweden (both preprint) are similar.

Pfizer-BioNTech announced (via press release) preliminary findings from their study on efficacy against the Omicron variant. This study identified sufficient neutralizing antibody titers among individuals who received 3 doses of the Pfizer-BioNTech vaccine, but there was a 25-fold reduction in neutralizing capacity for individuals who received only 2 doses of the Pfizer-BioNTech vaccine. Notably, these findings are based on the volume of neutralizing antibodies against the Omicron variant present in the sera, and not a direct assessment of efficacy against the variant.

These studies provide initial insight into the efficacy of existing SARS-CoV-2 vaccines against the emerging Omicron variant, but we currently only have data from small, in vitro laboratory studies on which to base these analyses. The in vivo immune response varies widely, and it is unclear exactly how the current vaccines will function among the broader public or to what degree booster doses are necessary to provide sufficient protection. Current evidence suggests that existing vaccines may be less effective against the Omicron variant, but some experts indicate that fully vaccinated individuals would likely maintain some protection against severe disease. Larger studies among vaccinated individuals are necessary to gain the necessary insight.

In a likely effort to help control the Omicron variant, the US FDA today expanded its authorization for booster doses of the Pfizer-BioNTech vaccine to 16- and 17-year-olds, available 6 months after their initial 2-dose series. The CDC is expected to make formal recommendations soon, possibly today. Additionally, the WHO today recommended that only people who are immunocompromised or who received an inactivated SARS-CoV-2 vaccine receive a third vaccine dose after a primary 2-dose series. The WHO is not yet recommending third or booster doses for all vaccine recipients in order to promote equity in the global distribution of vaccines.

Dr. Mike Ryan, Director of the WHO’s Health Emergencies Programme, addressed speculation that the Omicron variant results in milder disease. He emphasized that while viruses tend to evolve to become more transmissible, the idea that a more transmissible virus results in milder symptoms is “an urban legend.” Even if the Omicron variant causes milder disease, increased transmission can put additional pressure on health systems. In addition to more patients with mild disease seeking care, milder disease that goes untreated can progress to more severe symptoms, and increased transmission can facilitate further mutations to the virus.