Early Data Suggest Omicron Could Push Out Delta

 Early data from one of the South African labs at the forefront of Omicron science suggested infection with that variant provides neutralizing immunity against the Delta variant as well.

In a small sample of 13 people who'd been infected with Omicron, neutralizing antibody titers against Omicron rose 14.4-fold over a 2-week period, according to Alex Sigal, PhD, of the Africa Health Research Institute in Durban, and colleagues.

Neutralizing antibody titers against Delta rose 4.4-fold during that time, they reported in a medRxiv submission that hasn't yet appeared on that website or been peer reviewed.

"If, as it currently looks like from the South African experience, Omicron is less pathogenic, then this will help push Delta out, as it should decrease the likelihood that someone infected with Omicron will get re-infected with Delta," Sigal said on Twitter.

"If that's true, then the disruption COVID-19 has caused in our lives may become less," he tweeted.

It's hopeful news for countries like the U.S. that are still struggling with an Omicron surge -- but it doesn't negate the likelihood of the development of future variants that may be immune-evading.

For their study, Sigal and colleagues enrolled 15 participants who were infected during the Omicron wave and whose infections were confirmed to be due to Omicron. All had been admitted to the hospital but only four required supplemental oxygen.

Two of the participants didn't detectably neutralize Omicron and were excluded from the analysis, leaving a total of 13 participants.

Of the 13, seven had been vaccinated: three with two doses of Pfizer and four with the Johnson & Johnson vaccine (one of whom had a booster of it as well).

Using a live virus neutralization assay, Sigal and colleagues measured participants' ability to neutralize Omicron and Delta both at enrollment (which was soon after symptom onset) and again at a median of 14 days later.

They found that Omicron neutralization rose from a geometric mean titer (GMT, as measured by FRNT50) of 20 to 285, for a 14.4-fold increase over those 2 weeks.

Titers against Delta rose from 80 to 354, for a 4.4-fold increase during that time, they reported.

This "may result in decreased ability of Delta to re-infect those individuals," they wrote. "Along with emerging data indicating that Omicron, at this time in the pandemic, is less pathogenic than Delta, such an outcome may have positive implications in terms of decreasing COVID-19 burden of severe disease."

However, they cautioned that participants in this study were likely to have been previously infected. In addition, more than half were vaccinated. Thus, they warned it's "unclear if what we observe is effective cross-neutralization of Delta virus by Omicron elicited antibodies, or activation of antibody immunity from previous infection and/or vaccination."

Sigal noted on Twitter that immunity to both variants was especially enhanced for those who had been vaccinated.

https://www.medpagetoday.com/infectiousdisease/covid19/96415