A version of this story appeared in the February 3 edition of CNN’s Coronavirus: Fact vs. Fiction newsletter. Sign up here to receive the need-to-know headlines every weekday.

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The Covid-19 vaccine developed by the University of Oxford and AstraZeneca not only prevents people from developing symptomatic coronavirus infections, but also appears to slow down transmission of the coronavirus, researchers reported on Tuesday.

The findings, released in a preprint paper that has not yet been peer reviewed, are the first evidence that a Covid-19 vaccine can reduce the virus’ spread, and underlines the importance of mass vaccination as a way out of the pandemic.

Researchers at the University of Oxford measured transmission by swabbing some participants every week to detect signs of the virus, and found that the rate of positive PCR tests declined by about half after two doses of the vaccine. If the vaccine were simply making infections more mild, PCR positivity would not change, the authors argued.

The study also found that a single shot of the Oxford-AstraZeneca vaccine provided 76% protection against symptomatic Covid-19 when the second shot was delayed by up to three months, supporting the vaccination plan rolled out by Britain and other countries stretching time between the first and second doses (Note: The data does not mean the same will be true for other vaccines).

The researchers said spacing doses by three months was “an effective strategy for reducing disease, and may be the optimal for rollout of a pandemic vaccine when supplies are limited in the short term.” That is good news, especially in the United Kingdom, where the race is on to vaccinate as much of the population as possible while a new, more transmissible variant spreads.

British authorities recently discovered that the variant first detected there had acquired a new mutation – one detected in strains in South Africa and Brazil – that could make vaccines less effective.

Meanwhile, a separate large British study looking at coronavirus infections in real life has confirmed what lab experiments had previously shown: Most people keep some antibodies to the virus for at least six months after recovery.

YOU ASKED. WE ANSWERED.

Q: Why do some people still test positive for Covid-19 after a vaccine?

A: A Covid-19 vaccine does not provide full or immediate protection, which means it’s still possible to get infected and test positive for the virus. Democratic Rep. Stephen Lynch of Massachusetts did. He tested positive after he got his second dose of the Pfizer vaccine. Hall of Fame basketball coach Rick Pitino, who coaches the men’s team at Iona College in New York, also tested positive after getting his first dose.

They could have tested positive for a number of reasons:

  • It takes a few days to a few weeks for the vaccine to work, according to the US Centers for Disease Control and Prevention.
  • The two US-authorized vaccines are highly effective (94-95%) but they don’t provide total protection.
  • Vaccination prevents disease, but it’s still unclear if, or how much, the vaccine prevents all infections.
  • Vaccines don’t work retroactively, e.g. they could have already contracted Covid-19.
  • There’s concern that certain variants that have been spreading in the US could be less susceptible to the protection that comes from vaccines.

Send your questions here. Are you a health care worker fighting Covid-19? Message us on WhatsApp about the challenges you’re facing: +1 347-322-0415.

WHAT’S IMPORTANT TODAY

British scientists say the next dangerous Covid variant is likely already out there

Almost a month into a third nationwide lockdown, most of England seems to be in hibernation: stores are shuttered, high streets are deserted and trains are almost empty. But in one small village in the countryside near Cambridge there is a hive of activity.

Dressed in white lab coats and surgical masks, staff at the Sanger Institute scurry from machine to machine – robots and giant computers that are so heavy, they’re placed on solid steel plates to support their weight. They’re much more than essential workers – right now, they’re doing some of the most important work on Earth: genetically sequencing the coronavirus. What are they looking for? Dangerous mutations that could make the pandemic much worse, Scott McLean and Florence Davey-Attlee report.

US to start distributing vaccines directly to pharmacies

The Biden administration announced Tuesday it will begin direct shipments of Covid-19 vaccines to retail pharmacies next week, expanding points of access for Americans to receive shots as concerns about variants of the virus expand.

Health experts have said it’s critical to expand the amount of locations Americans can visit to get vaccinated, both to streamline distribution efforts but also to ensure the vaccine is available to a wider swath of the public as vaccine disparities emerge. But adding new locations for vaccinations will only alleviate part of the problem. Vaccine supply remains extremely limited and the additional locations are likely to come as states are still clamoring for more doses.

WHO team visits China bat lab at the center of Covid conspiracies

A team of World Health Organization investigators visited a laboratory in Wuhan on Wednesday that has been the focus of conspiracies and speculation about the origin of the pandemic. Few places they are visiting are as controversial as the lab, run by the Wuhan Institute of Virology, which officials in former US President Donald Trump’s administration suggested, without providing evidence, could have been the origin of the coronavirus.

The lab, which is affiliated with the central government-run Chinese Academy of Sciences, is the only one in mainland China equipped for the highest level of biocontainment, known as Biosafety Level 4 (BSL-4). BSL-4 labs are designed to study the world’s most dangerous pathogens – those that pose a high risk for transmission, are frequently fatal and most often have no reliable cure, such as coronaviruses, James Griffiths and Sandi Sidhu write.

Study finds Russian vaccine has 91.6% efficacy

After criticism last year for an early rollout, Russia’s Sputnik V vaccine is 91.6% effective against symptomatic Covid-19 and 100% effective against severe and moderate disease, according to an interim analysis of Phase 3 trial results published in The Lancet.

The results deliver a big geopolitical victory for Moscow, as well as a potential piece of the global vaccine market pie. Sputnik V joins only two other vaccines whose efficacy is higher than 90%, but unlike Pfizer and Moderna’s shots, the Russian vaccine is cheaper and can be stored at normal fridge temperatures.

Praising the “good data,” German Chancellor Angela Merkel told German public broadcaster ARD on Tuesday that “every vaccine is welcome in the European Union.”

ON OUR RADAR

  • More people in the US have now received one vaccine dose than have been infected with Covid-19, CDC says.
  • A newly 75-year-old Dolly Parton has not gotten her Covid-19 shot yet, despite donating $1 million to vaccine development.
  • Shut out by allies, Canada will produce its own vaccines by the end of 2021.
  • More than half of the population of the Indian capital region Delhi have been infected with Covid-19.

TOP TIP

The day has finally come. You’ve received the second dose of a Covid-19 vaccine. Does that mean you’re free to go about life as you did before the pandemic once immunity kicks in? Not exactly. There are still safety precautions you need to follow in order to keep you, your loved ones and everyone else safe and protected from the virus.

Wondering when you can stop wearing a mask, eat inside a restaurant, travel, go to sporting events and concerts, or freely visit friends and family? CNN spoke to experts to find out.

TODAY’S PODCAST

“History is important, especially as it pertains to vaccine hesitancy. I think the important aspect of both Tuskegee and Henrietta Lacks is that there was a lack of forthrightness and lack of transparency and that impacted those involved.” – Dr. Leon McDougle, president of the National Medical Association

Inequities and racism continue to exist within the US healthcare system and profoundly impact Black communities. It’s a complex history that’s often misunderstood. CNN Chief Medical Correspondent Dr. Sanjay Gupta talks to Dr.  McDougle about how the past can shine some light on the challenges of reaching Black Americans with the Covid-19 vaccine. Listen now.