Is it time to delay second doses of coronavirus vaccines?


By Maggie Fox | CNN

Two letters to major medical journals this week provide fuel for the argument that in these times of scarce coronavirus vaccine, people can skip their second doses, immediately doubling the supply for others.

In one, researchers at Israel’s largest hospital watched what happened when more than 7,000 staff there got vaccinated. In between their first and second doses of the Pfizer/BioNTech vaccine, rates of infected plummeted. By the second to fourth week after the first shot, rates of symptomatic infection were down by 85%.

In a second, Canadian researchers found evidence of more than 90% protection after a single dose of the Pfizer/BioNTech vaccine.

It’s not at all clear how long this protection would last, and both the Pfizer and Moderna vaccines were tested and authorized on the basis of a two-dose regimen. The companies, the US Food and Drug Administration, and top government officials including National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci have cautioned against going outside what’s known and tested.

“People need to continue to get their second shot,” Andy Slavitt, White House senior adviser on the Covid-19 response, told CNN’s Chris Cuomo Thursday night. “The second shot does add significantly to their immunity, and what we have to do is, we have to get more quickly through our first doses that we have in the field, but no one is advising people to skip their second shot at this point.”

But the US is struggling to get even first doses into the population, and is watching the death toll from the virus climb steadily towards 500,000. While US federal officials at first said they hoped anyone who wanted a vaccine could get one by April, they have now pushed back that timeline to July.

And new variants that appear to make the virus more contagious are popping up around the world and across the country. It’s possible they could fuel a resurgence in the spread of the virus long before 70% to 85% of the population — the percentage Fauci estimates is needed to achieve herd immunity — can get vaccinated.

The Israeli findings, released as a letter to The Lancet medical journal, involve 9,000 health care workers at Tel Aviv’s Sheba Medical Center, more than 7,000 of whom were vaccinated by the end of January.

The team looked at the rate of infections during the three weeks or so before the workers got a second dose of vaccine. They found a 47% reduction in symptomatic coronavirus infections among the health care workers during the first two weeks after the first shot, and an 85% reduction over the following two weeks.

“Our data show substantial early reductions in SARS-CoV-2 infection and symptomatic COVID-19 rates following first vaccine dose administration,” Dr. Eyal Leshem and colleagues wrote.

“Early reductions of COVID-19 rates provide support of delaying the second dose in countries facing vaccine shortages and scarce resources, so as to allow higher population coverage with a single dose.”

Dr. Danuta Skowronski of the British Columbia Centre for Disease Control, …read more

Source:: The Mercury News – Entertainment


(Visited 7 times, 1 visits today)

Leave a Reply

Your email address will not be published. Required fields are marked *