The U.S. Centers for Disease Control and Prevention (CDC) has disagreed with the agency’s director, Rochelle Walensky, who asserted that people vaccinated against COVID-19 don’t spread the infection.
“Dr. Walensky spoke broadly,” a CDC spokesperson told the New York Times. “It’s possible that some people who are fully vaccinated could get COVID-19. The evidence isn’t clear whether they can spread the virus to others.”
Walensky made her comments based on a CDC study released last week. The study conducted nose swab tests on health care workers, emergency crews, and frontline workers every week for 13 weeks. It found vaccines were 90 per cent effective against SARS-CoV-2 two weeks after the second dose.
“Our data from the CDC today suggests, you know, that vaccinated people do not carry the virus, don’t get sick,” Walensky said on MSNBC last weekend, adding “that is not just in the clinical trials, but it’s also in real world data.”
She also said wearing masks and following safety protocols should continue.
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Walensky’s comment was widely taken to suggest that people vaccinated against COVID-19 aren’t spreaders, causing a flap among scientists who argued in the Times that the the research is inconclusive and it’s still unclear whether that’s the case.
“It’s much harder for vaccinated people to get infected, but don’t think for one second that they cannot get infected,” Paul Duprex, director of the Center for Vaccine Research at the University of Pittsburgh, told the paper.
“If Dr. Walensky had said most vaccinated people do not carry the virus, we would not be having this discussion,” added John Moore, a virologist at Weill Cornell Medicine in New York.
“What we know is the vaccines are very substantially effective against infection — there’s more and more data on that — but nothing is 100 percent,” he said. “It is an important public health message that needs to be gotten right.”
Needs to be gotten right
The reversal highlights the challenge that public health experts face as vaccine distribution gathers pace — the expectation to ease recommendations while the research is still evolving.
While the Pfizer and Moderna vaccines have shown high efficacy in preventing COVID-19, it’s too early to tell whether immunization makes people less contagious, scientists said.
“There cannot be any daylight between what the research shows — really impressive, but incomplete protection — and how it is described,” advised Dr. Peter Bach, director of the Center for Health Policy and Outcomes at Memorial Sloan Kettering Cancer Center advised.
“This opens the door to the skeptics who think the government is sugarcoating the science,” he said, “and completely undermines any remaining argument why people should keep wearing masks after being vaccinated.”
CDC guidelines allow fully vaccinated people to visit others who are fully vaccinated without masks or physical distancing if they are at low risk for severe COVID-19. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated-guidance.html
Fully vaccinated travelers also don’t need to test for coronavirus before and after domestic flights or before international travel, nor is self-quarantining after arriving necessary.
However, it’s too soon for anyone to toss out their face covering of choice. Public health experts advise even the inoculated mask up in public while their risk of asymptomatic spread remains unknown.
“A growing body of evidence suggests that fully vaccinated people are less likely to have asymptomatic infection and potentially less likely to transmit,” the CDC website states.
“However, further investigation is ongoing.”
Protection against transmission
In March, Pfizer reported its COVID-19 vaccine was 94 per cent effective in preventing asymptomatic transmission of SARS-CoV-2, according to data collected from Jan.17 to March 6 in Israel.
In extremely rare cases, fully vaccinated people have tested positive. A study published in the New England Journal of Medicine reported a positivity rate of .05 per out of almost 36,659 health care workers in two California campuses from Dec. 16, 2020 to Feb. 9.
As of yesterday (April 6), about 19 per cent of the U.S. has been fully vaccinated.
Data collected by the CDC found vaccines in the U.S. were administered at a rate of 3 million a day, based on a seven day average. Last week, CDC reported COVID-19 was the underlying cause in 345,323 deaths in the US in 2020, making it the third leading cause of death, behind heart disease and cancer.
In a press briefing on April 2, Walensky urged the public to be cautious regardless of their immunization status.
“Continue to take prevention measures in public and adhere to our guidance on ways to reduce the spread of COVID-19: Wear a mask, physically distance, avoid crowds and poorly ventilated areas, and wash your hands frequently,” she said. “We will continue to monitor the evidence and provide updates as we learn more.”