SARS-CoV-2 antibody levels predict COVID vaccine efficacy, study finds

SARS-CoV-2 antibody concentrations predict COVID-19 vaccine effectiveness, with higher levels correlating with greater protection, according to an ongoing US phase 3 clinical trial yesterday in Science.

A team led by researchers from Fred Hutchinson Cancer Research Center in Seattle evaluated 30,420 adult recipients of the Moderna mRNA COVID-19 vaccine at 99 centers for neutralizing and binding antibodies as correlates of risk for, and protection against, infection.

They measured the antibodies at the second vaccine dose and then again 4 weeks later. Concentrations were inversely associated with COVID-19 infection risk and directly tied to vaccine efficacy.

Vaccine effectiveness in vaccinees with 50% neutralizing antibody levels of 10, 100, and 1,000 international units per milliliter was 78% (95% confidence interval [CI], 54 to 89%), 91% (95% CI, 87% to 94%), and 96% (95% CI, 94% to 98%), respectively.

Based on antibody levels, the estimated risk of SARS-CoV-2 infection was roughly 10 times lower for vaccinees whose antibody concentrations were in the top 10% of values, relative to those with negative or undetectable values.

The results help define immune marker correlates of protection, or biomarkers to measure how much immunity is needed to prevent COVID-19 infection, the study authors said. Identifying and validating a correlate of protection would expedite vaccine research and regulatory approval for existing vaccines for new groups of people, modifications of vaccine regimens, and new vaccines, they added.

“Our findings that all evaluated binding and neutralizing antibody markers strongly inversely correlated with COVID-19 risk, and directly correlated with vaccine efficacy, adds evidence toward establishing an immune marker surrogate endpoint for mRNA COVID-19 vaccines,” the researchers wrote.
Nov 23 Science study


Study: 1 in 5 people avoided healthcare during initial COVID-19 lockdown

A study yesterday in PLOS Medicine shows that up to 20% of people polled in the Netherlands avoided seeking healthcare during the initial months of the COVID-19 pandemic, even for serious health concerns.

The study is based on results from 5,656 participants of the Rotterdam Study, who answered questions on healthcare from April 2020 to July 2020. The study is an ongoing effort to assess chronic diseases in mid to late life.

One in five participants (20.2%) reported avoiding healthcare during the pandemic. Of those, 36.3% reported symptoms that warranted urgent care, including limb weakness (13.6%), heart palpitations (10.8%) and chest pain (10.2%). Adjusted odds ratios showed women were more likely to avoid care (1.58; 95% confidence interval [CI], 1.38 to 1.82), as were those with poor self-appreciated health (per-level decrease, 2.00; 95% CI, 1.80 to 2.22).

High rates of depression were also related to avoiding healthcare.

In a PLOS press release, senior author Silvan Licher said, “One in five avoided healthcare during COVID-19 lockdown, often with alarming symptoms like chest pain or limb weakness. Vulnerable citizens were mainly affected, emphasising the urgent need for targeted public education.” 
Nov 23 PLOS Medicine
Nov 23 PLOS press

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