Research Highlights Importance of full Vaccination, Concerns Around Delta Variant

Two doses of the Pfizer or AstraZeneca vaccines generated high sero-neutralization against the strain.

Recent research conducted by a team of investigators from France has shown that the Delta variant of the SARS-CoV-2 virus has certain mutations which allow it to evade some of the neutralizing antibodies produced by vaccines, a natural infection and other therapies, which may help explain its rapid spread.

However, the investigators discovered that 2 shots of the Pfizer-BioNTech or AstraZeneca vaccines generated a neutralizing response in 95% of individuals.

Levels of neutralizing antibodies are typically predictive of immune protection from symptomatic infection.

An article discussing the data was published on Thursday in the journal Nature.

The Delta variant was first identified in India in October 2020 and is now the dominant strain in many countries around the world. Delta is believed to be around 60% more transmissible than the Alpha variant that spread through much of Europe earlier this year.

Although the vaccines have so far been effective against the virus, the growing number of variants are beginning to concern public health experts and officials. While no strains seem to be causing more severe disease, they are progressively more transmissible than the original virus that emerged in Wuhan, China.

In the United States, the Centers for Disease Control and Prevention (CDC) estimated that 51.7% of new infections nationally were the Delta variant, 5 times the prevalence of 4 weeks ago.

For the study, the French investigators isolated an infectious Delta strain from a traveler returning from India. They then examined the variants sensitivity to monoclonal antibodies and antibodies present in sera from COVID-19 convalescent individuals or vaccine recipients.

They found that monoclonal antibodies, such as Bamlavinimab, lost their binding to the viral spike protein and no longer neutralized the variant. They also found that Delta is less sensitive to sera from naturally immunized individuals and that vaccination boosted their humoral immune response.

Additionally, a single dose of vaccine in those who were not previously infected barely induced neutralized antibodies, but 2 doses generated high sero-neutralization. The efficacy for the Pfizer and AstraZeneca vaccines against the variant were 88% and 60%, respectively.

With each new variant that contains a unique set of mutations, the need for more people to be vaccinated grows.

“We’ve seen the virus evolving to get better and better at human transmission. I would expect that process will sort of plateau,” Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center in Seattle said. “But I don’t think the evolution will stop. Because I think there is a sort of endless potential for the virus to get mutations to escape from antibodies.”