Existing COVID-19 vaccines and boosters are not enough to secure long-term protection from the new omicron variants, a new study has found.

Sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) and led by the Infectious Diseases Clinical Research Consortium, researchers conducted a study on the neutralizing antibodies elicited by the different COVID vaccine-and-booster combinations.

The team did a “mix and match” clinical trial wherein participating adults were administered boosters after completing a primary COVID-19 vaccination series. Regardless of the combinations, the researchers measured the immune responses yielded in every setup.

Previous results reported in the New England Journal of Medicine showed that all combinations led to increased neutralizing antibody levels in the recipients.

For the new analysis, the team evaluated how the neutralizing antibodies fared against the different omicron sub-lineages, including BA.1, BA.2.12.1, and BA.4/BA.5.

Published in Cell Reports Medicine this week, the findings of the more recent analysis determined that the antibody levels of the group that received the Johnson & Johnson vaccine and booster were low.

On the other hand, combinations that utilized Moderna and Pfizer vaccines and boosters triggered high levels of neutralizing antibodies against the omicron BA.1 sub-lineage.

The researchers also noticed that the neutralizing antibodies substantially decreased in three months in all group combinations. The antibody levels dropped 2.4 to 5.3-fold three months after the booster shot.

“We assess the magnitude and short-term durability of neutralizing antibodies after homologous and heterologous boosting with mRNA (Pfizer and Moderna) and Ad26.COV2.S (Janssen) vaccines. All prime-boost combinations substantially increase the neutralization titers to omicron, although the boosted titers decline rapidly within 2 months from the peak response compared with boosted titers against the prototypic D614G variant,” the researchers wrote.

The omicron BA.2 and BA.4/BA.5 sub-lineages were 1.5 and 2.5 times less susceptible to neutralization. This reflected the real-world reports about the newer strains. BA.5 is currently the dominant strain in the U.S.

“These results have implications for boosting requirements to protect against omicron and future variants of SARS-CoV-2,” the team indicated in their study.

The data could also be used for making informed decisions about future vaccine schedule recommendations and the need for additional variant vaccine boosting, according to the National Institutes of Health.