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 Rapid antigen tests may be unreliable in children
When used in children, rapid antigen tests for detecting the
coronavirus do not meet accuracy criteria set by the World Health
Organization and U.S. and UK device regulators, according to
researchers who reviewed 17 studies of the tests.
The trials evaluated six brands of tests in more than 6,300 children
and teenagers through May 2021. In all but one study, the tests were
administered by trained workers. Overall, compared to PCR tests, the
antigen tests failed to detect the virus in 36% of infected
children, the researchers reported on Tuesday in BMJ Evidence-Based
Medicine. Among children with symptoms, it missed 28% of infections.
Among infected kids without symptoms, the tests missed the virus in
44%. Only about 1% of the time did the tests mistakenly diagnose the
virus in a child who was not actually infected.
Given that more than 500 antigen tests are available in Europe
alone, the authors said, "the performance of most antigen tests
under real-life conditions remains unknown." But the new findings
"cast doubt on the effectiveness" of rapid antigen tests for
widespread testing in schools, they concluded.
Breastmilk transmission of COVID-19 unlikely
A new study appears to confirm smaller, earlier studies that
suggested nursing mothers are unlikely to transmit the coronavirus
in breastmilk.
Between March and September 2020, researchers obtained multiple
breastmilk samples from 110 lactating women, including 65 with
positive COVID-19 tests, 36 with symptoms who had not been tested,
and a control group of 9 women with negative COVID-19 tests. Seven
women (6%) - six with positive tests and one who had not been tested
- had non-infectious genetic material (RNA) from the virus in their
breastmilk, but none of the samples had any evidence of active
virus, according to a report published on Wednesday in Pediatric
Research. Why breastmilk would contain coronavirus RNA but not
infectious virus is unclear, said study leader Dr. Paul Krogstad of
the David Geffen School of Medicine at UCLA, "Breastmilk is known to
contain protective factors against infection, including antibodies
that reflect both the mother's exposure to viruses and other
infectious agents and to vaccines she has received," he noted.
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 The U.S. Centers for Disease
Control and Prevention (CDC) advises that before
breastfeeding, bottle-feeding, or expressing
milk, women with COVID-19 should wash their
hands or use hand sanitizer with at least 60%
alcohol. The CDC also recommends that they wear
a mask when within 6 feet (1.8 meters) of the
baby.
New technique may speed vaccine, antibody drug
development
Researchers are working on a way to speed
development of vaccines and monoclonal antibody
drugs for COVID-19 and other illnesses,
shortening the time from collection of
volunteers' blood samples to identification of
potentially useful antibodies from months to
weeks.
As described in Science Advances on Wednesday,
the new technique employs cryo-electron
microscopy, or cryoEM, which involves freezing
the biological sample to view it with the least
possible distortion. Currently, "generation of
monoclonal antibodies involves several steps, is
expensive, and typically takes somewhere on the
order of two to three months, and at the end of
that process you still need to perform
structural analysis of the antibodies" to figure
out where they attach themselves to their
target, and how they actually work, explained
Andrew Ward of Scripps Research Institute in La
Jolla, California.
In experiments using the new approach to look
for antibodies to HIV, "we flipped the process
on its head... by starting with structure," Ward
said. Because cryoEM affords such high
resolution, instead of having to laboriously
sort through antibody-producing immune cells one
by one to identify promising antibodies, the
process of identifying antibodies, mapping their
structure and seeing how they are likely to
attack viruses and other targets goes much
faster, he added. "The ongoing COVID-19 pandemic
has highlighted the need for such robust and
rapid technologies," his team concluded.
Click for a Reuters graphic on vaccines in
development.
(Reporting by Nancy Lapid; Editing by Bill
Berkrot)
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