Sourced from the web by Tracy Cabrera
As reports confirm that vaccines largely prevent people from getting sick, another question is emerging: do they also block infection? This has not been fully answered, according to health experts. The file photo shows a nurse administering a vaccine to a patient in England.
CAMBRIDGE, MASSACHUSETTS — With reports coming in from Scotland and Israel—where much or most of the population have gotten Covid vaccine jabs—confirmation have been seen that vaccines largely prevent people from getting sick but another question is whether they also block infection?
A lot depends on the answer, experts claim.
“If vaccines being rolled out worldwide ward off not only symptoms but the virus itself, it could sharply slow the pathogen’s spread and hasten the return to normalcy,” they said.
“If the true impact on infections was very high, it would be great news because that is what we need for herd immunity,” Center for Communicable Disease Dynamics director at the Harvard T.H. Chan School of Public Health Marc Lipsitch pointed out.
Herd immunity is achieved when most of a population — estimates vary between 60 to 80 percent—have acquired defenses against the coronavirus, whether through vaccination or because they caught the bug and survived.
“But if the Pfizer, Moderna and AstraZeneca vaccines—and perhaps others made in China, Russia and India—shield poorly against infection, then even people who have rolled up their sleeves to be injected remain potential, unwitting carriers,” Lipsitch noted.
“The big concern is that the vaccines prevent illness, hospitalization and death, but won’t sufficiently prevent transmission,” UK-based consultant in communicable disease control and British Medical Association’s Public Health Medicine Committee chair Peter English added.
In that scenario, English said communities and economies already reeling from the pandemic face prolonged mask-wearing, social distancing and more-or-less hard lockdowns until vaccine campaigns can be completed.
“There is also a greater risk that vaccine ‘escape variants’ might be thrown up as the virus continues to circulate,” he warned.
Several such variants—more contagious, more deadly or both — have already proliferated in England, South Africa and Brazil as the SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) virus finds it harder to find new hosts, a predictable phase in the evolution of a pandemic.
But recent studies along with others in the pipeline give reason for optimism. Research covering the entire Scottish population of 5.4 million—a fifth inoculated with the Pfizer or Oxford/AstraZeneca jabs—provides real-world validation that the vaccines prevent Covid symptoms and illness more than 90 percent of the time.
A study that compared two groups in Israel of nearly 600,000 persons each—one vaccinated and the other not—also reported reduced illness in line with clinical trials. But unlike the research from Scotland, the Israeli findings also showed infections had sharply declined in the vaccinated cohort—by 92 percent among those at least one week past the second of two doses.
The true level of protection may not be that high because Israel does not systematically test for Covid among people with no symptoms, the authors acknowledge.
“They are likely to have failed to detect some asymptomatic cases, and we know that people without symptoms can still transmit the infection,” English revealed.
But the results are still encouraging, he added.
“These findings give us hope that vaccination alone may get the R number below 1,” the communicable disease expert said in referral to the threshold above which a virus continues to spread.
“If it can—and this is the big question—we would eventually no longer need to take behavioral measures such as lockdowns or masks to interrupt spread,” he concluded. (AI/MTVN)