The immune responses to the Omicron variant waned substantially with neutralizing antibody levels decreasing 2.4- to 5.3-fold by 3 months after the booster dose.
Although COVID-19 boosters have been found to elicit high levels of neutralizing antibodies against the Omicron variant, the antibody levels decrease substantially within 3 months, according to findings published in Cell Reports Medicine.1
As part of a clinical trial designed to evaluate immune responses over time, individuals in the study received the same vaccine as their primary series while others received a different vaccine.1
The combination of vaccines includes 2 doses of the mRNA-1273 vaccine, 28 days apart with a booster of mRNA-1273 in the 100 microgram strength; 2 doses of the mRNA-1273 vaccine, 28 days apart with a booster of mRNA-1273 in the 50 microgram strength; 1 dose of Ad26.COV2.S with the same vaccine as a booster; 1 dose of Ad26.COV2.S with BNT162b2 as a booster; 2 doses of BNT162b2, administered 21 days apart, with the same as a booster; and 2 doses of BNT162b2, administered 21 days apart, with Ad26.COV2.S as a booster.1
The results of this part of the study, published in the New England Journal of Medicine, showed that all combinations of primary and booster vaccines resulted in increased neutralizing antibody levels in the individuals who received them.1
As part of the new analysis, investigators reported that nearly all of the vaccine combinations evaluated elicited high levels of neutralizing antibodies to the Omicron BA.1 sub-lineage; however, the antibody levels against the Omicron variant were low in the group who received Ad26.COV2.S (Johnson & Johnson) as both a primary and booster vaccine.1
Furthermore, the immune responses to the Omicron variant in all groups waned substantially, with neutralizing antibody levels decreasing 2.4- to 5.3-fold by 3 months after the booster dose.1
Additionally, the Omicron sub-lineages BA.2 12.1 and BA.4/5 were 1.5 and 2.5 less susceptible to neutralizing, respectively, compared to the BA.1 sub-lineage. For both linages, they were also 7.5 and 12.4 times less susceptible compared to the ancestral strain, respectively.1 BA.5 is the current dominant variant in the United States.1
The investigators said that the findings were consistent with real-world reports that showed waning protection against COVID-19 during the Omicron wave in individuals who received a primary and booster dose. The immune response to Omicron sub-lineages showed reduced susceptibility to these rapidly emerging subvariants.1
These data could be used to inform future decisions regarding vaccine schedule recommendations, including the need for variant vaccine boosting.1
Additional studies have shown that a second booster dose protects against Omicron subvariants, including results of a study published in Science and a study led by the CDC.
Current recommendations from the CDC include a second booster dose, a fourth vaccine in a 2-dose series, for individuals who are 50 years of age and older, as well as those who are 12 years of age and older who are moderately or severely immunocompromised.2
Reference
- Vaccine-induced immune response to Omicron wanes substantially over time. News release. National Institutes of Health. July 19, 2022. Accessed July 25, 2022. https://www.nih.gov/news-events/news-releases/vaccine-induced-immune-response-omicron-wanes-substantially-over-time
- Second mRNA booster significantly effective against Omicron variants, study finds. News release. Science Daily. July 18, 2022. Accessed July 25, 2022. https://www.sciencedaily.com/releases/2022/07/220718094524.htm
