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 Drugstore COVID-19 tests predict short-term infectiousness
Drugstore rapid COVID-19 tests, less sensitive than gold-standard
PCR tests, might yield a negative result in 15 minutes while failing
to detect virus particles but those same particles might pose no
risk of transmission in the very short term, according to a report
posted on Thursday on medRxiv ahead of peer review.
The researchers first performed these antigen tests on swab samples
from 181 individuals with PCR-confirmed SARS-CoV-2 infections. Next,
they took the virus from the swabs and tried to grow it in test
tubes. When viral loads were below the antigen tests' level of
detection, the virus particles were often incapable of growing.
People with low viral loads and negative antigen tests may become
infectious "a day or two or three days later," said Dr. James Kirby
of Beth Israel Deaconess Medical Center in Boston. "Therefore, to be
most effective, antigen tests should be used immediately before an
event or contact with those at greater risk from infection." The
swabs must be collected for testing carefully, following the
instructions provided with the testing kits, he added. "In other
words, you want a really good sampling of the inside of your nose."
Breakthrough COVID-19 often severe in cancer patients
Vaccinated people with cancer should not underestimate their risks
from breakthrough cases of COVID-19, researchers warn.
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 Among 54 cancer patients who
became infected despite receiving a two-dose
vaccine from Moderna or Pfizer/BioNTech or a
single-dose vaccine from Johnson & Johnson -
before booster doses were recommended - 65%
needed to be hospitalized, 19% ended up in
intensive care units, and 13% died, according to
data from the international COVID-19 and Cancer
Consortium.
The study did not analyze the vaccines' efficacy at
preventing infections in the first place. But among those who did
become infected, COVID-19 was no less severe than it was in a
comparison group of 1,656 unvaccinated cancer patients with
COVID-19, researchers reported on Friday in Annals of Oncology. The
risks were greatest for patients with blood cancers.
"Many studies ... have suggested that patients with cancer don't
create a strong immune response, and this is the first large study
that likely shows the consequences of this," said Dr. Jeremy Warner
of Vanderbilt University in Nashville, Tennessee. "Additional doses
and boosters are critical, as are continued masking, social
distancing, and encouragement of all close contacts of patients with
cancer to get vaccinated."
Click for a Reuters graphic https://tmsnrt.rs/3c7R3Bl on vaccines in
development.
(Reporting by Nancy Lapid; Editing by Howard Goller)
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