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Photo: Faris Hadziq/SOPA Images/LightRocket via Getty Images

Increasing the number of coronavirus tests performed relative to a country's caseload was the strategy most associated with reducing the transmission rate of the virus, according to a new study published in Health Affairs.

Yes, but: The U.S. overall had a low testing intensity between March and June, which means that "testing mostly diagnosed and isolated the most symptomatic cases, which has limited impact on transmission."

  • Even though we're now doing more than a million tests a day, it's not enough to keep up with our ever-rising caseloads.

Details: A tenfold increase in the ratio of tests to new cases reduced average transmission by 9%, the study found.

Between the lines: "Around half or more of COVID-19 transmission is caused by people who are asymptomatic or who have only minor symptoms, so only increases in PCR testing make it possible to increase detection and isolation of infectious cases, and then to increase the numbers of their potentially infectious contacts who are isolated," the authors write.

  • "This remains the only known approach that blocks person-to-person transmission sufficiently to stop the epidemic."

Bonus: The study also found that "being a US territory was also significantly associated with a 12.7% ... increase in transmissibility compared to the rest of the world."

Go deeper

Updated 12 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Vaccines: CDC director maintains Pfizer booster recommendation for high-risk workers — CDC director approves Pfizer boosters, adds eligibility for high-risk workers — FDA approves Pfizer boosters for high-risk individuals, people 65 and up.
  2. Health: America's mismatched COVID fears — Some experts see signs of hope as cases fall — WHO: Nearly 1 in 4 Afghan COVID hospitals shut after Taliban takeover — D.C. goes further than area counties with vaccine mandates.
  3. Politics: Bolsonaro isolating after health minister tests positive at UN summit — United Airlines says 97% of U.S. employees fully vaccinated — Mormon Church to mandate masks in temples.
  4. Education: Health care workers and teachers caught up in booster confusion — Asymptomatic Florida students exposed to COVID no longer have to quarantine — Education Department investigating Texas mask mandate ban.
  5. Variant tracker: Where different strains are spreading.
Jan 30, 2021 - World

Germany to impose travel restrictions to curb spread of coronavirus variants

Border police officers check passports and COVID-19 tests at Frankfurt Airport. Photo: Thomas Lohnes via Getty Images

Germany announced Friday that it was imposing new travel restrictions in an effort to curb the spread of more contagious coronavirus variants.

Details: All non-German residents traveling from countries deemed "areas of variant concern," including the United Kingdom, South Africa, Portugal, Ireland, Brazil, Lesotho and Eswatini, will be banned from entering the country, even if they test negative for the coronavirus.

Jan 29, 2021 - Health

J&J says its one-shot vaccine is 66% effective against moderate to severe COVID

Photo: Thiago Prudêncio/SOPA Images/LightRocket via Getty Images

Johnson & Johnson announced Friday that its single-shot coronavirus vaccine was 66% effective in protecting against moderate to severe COVID-19 disease in Phase 3 trials, which was comprised of nearly 44,000 participants across eight countries.

Between the lines: The vaccine was 72% effective in the U.S., but only 57% effective in South Africa, where a more contagious variant has been spreading. It prevented 85% of severe infections and 100% of hospitalizations and deaths, according to the company.