The United Kingdom's Heath Security Agency (HSA) recently posted a technical briefing on the highly mutated Omicron BA.2.86 variant, which said that, based on moderate confidence, the level of antibody escape is probably similar to XBB.1.5. In addition, data from two labs suggests it may have slightly higher ACE2 binding affinity, a factor that might play a role in transmissibility.

So far, there's no sign that infections involving BA.2.86 are more severe.

The virus is circulating among a mix of other variants, and so far the low number of sequenced viruses doesn't provide enough information to say if BA.2.86 will outcompete other viruses, but the HSA said it's plausible that its incidence may increase.

As of September 18, the UK had reported 43 BA.2.86 sequences, reflecting an increase of 11 from the week before. Ten people were hospitalized and six had unknown hospitalization status. No deaths from BA.2.86 were reported. The sporadic cases were reported from nearly all regions in people with no recent travel history. Other than an earlier reported nursing home cluster of 30 cases, only 2 other cases had epidemiological links.

Globally, as of September 18, there were 139 sequences from 137 human cases from 15 countries, according to the HSA. The largest portion are from the UK and France, followed by South Africa, Sweden, and the United States.

Three Pfizer/BioNTech COVID-19 vaccine doses stimulate long-term immune responses against SARS-CoV-2 similar to breakthrough infection plus two doses, while four doses only temporarily increase antibody levels, according to a new study in the International Journal of Infectious Diseases.

Every 2 to 4 months, researchers at Ziv Medical Center in Israel measured anti-spike SARS-CoV-2 immunoglobulin G (IgG) levels in healthcare workers (HCWs) who received at least two Pfizer COVID-19 doses and either had more doses and/or were infected up to 22 months after the second dose.

The study, which ended in September 2022, was a follow-up to one published in Clinical Infectious Diseases in March 2022.

Fourth dose may be best suited for high-risk groups

Most workers (62%) had received three COVID-19 vaccine doses, while 16% received two, 14% had four, and 8% had one, of whom 70 were vaccinated after infection.

Among 993 HCWs, infection after dose two led to higher IgG geometric mean titers (GMCs) than receipt of a third dose (4,285 vs 2,845 arbitrary units per milliliter [mL] 1 or 2 months after infection or vaccination).

The role of the fourth dose is different and may be more suited to providing additional short-term protection to individuals at high risk of severe outcomes, or during times of increased risk of exposure, such as periods of intense transmission.

Sixteen to 18 months after dose two, HCWs who were infected or received three or four vaccine doses had IgG GMCs higher than 500 arbitrary unit/ml, with no significant between-group differences. IgG levels leveled off 16 to 22 months after the second dose.

IgG levels surpassed the correlate of protection against the wild-type and Delta strains, but it's unclear clear how they stack up to those required against Omicron strains, which are probably much higher considering the lower effectiveness of the original Pfizer vaccine against Omicron, the researchers said.

Four to 6 months after a fourth dose, IgG levels had regressed to three-dose levels.

"The role of the fourth dose is different and may be more suited to providing additional short-term protection to individuals at high risk of severe outcomes, or during times of increased risk of exposure, such as periods of intense transmission," the study authors wrote.

The Centers for Disease Control and Prevention (CDC) last week announced $262 million in funding over next 5 years to 13 recipients to establish its first national network for detecting and responding more efficiently to public health emergencies.

Called the National Network for Outbreak Response and Disease Modeling, the program reflects representation from state health departments, tribal organizations, and the private sector. Eleven of the 13 recipients are universities, including, for example, the University of Minnesota, Johns Hopkins University, and Emory University.

The institutions will work as a network to conduct landscape analysis to identify gaps, needs, and opportunities for outbreak analytics and disease modeling. They will also pilot and implement analytic technologies and prepare for and response to infectious disease threats.

Dylan George, PhD, who directs the CDC's Center for Forecasting and Outbreak Analytics, said collaboration over the last year has been crucial for delivering decision support to leaders and improving outbreak response. "Building upon that experience by establishing this national network will help us better respond to outbreaks and prevent pandemics in the future," he said.