quote:

The U.K.’s decision to delay the second shot of the AstraZeneca-University of Oxford coronavirus vaccine has been found to be an effective strategy, according to a new study.

Oxford researchers found that the Covid vaccine was 76% effective at preventing symptomatic infection for three months after a single dose, and in fact that the efficacy rate rose with a longer interval between the first and second doses.

A delay in the second dose means more people can get their first vaccines sooner because it eases a tight supply.

“Vaccine efficacy after a single standard dose of vaccine from day 22 to day 90 post vaccination was 76% ... and modelled analysis indicated that protection did not wane during this initial 3 month period,” the study found. It was published on Tuesday as a preprint and is under review at The Lancet medical journal.

The efficacy rate rose to 82.4% when there was at least a 12-week interval before the second dose. When the second dose was given less than six weeks after the first one, the efficacy rate was 54.9%.

“These analyses show that higher vaccine efficacy is obtained with a longer interval between the first and second dose, and that a single dose of vaccine is highly efficacious in the first 90 days, providing further support for current policy,” the report said.

quote:

As the world races to vaccinate and fight new variants of Covid-19, a new trial is trying something that could speed up the process: mixing shots.

Patients taking part in a clinical trial launched Thursday in the United Kingdom will receive different vaccines for their first and second doses: the vaccine developed by Oxford University and AstraZeneca, followed by the one from Pfizer and BioNTech, or vice versa.

The U.K.'s Department of Health said it was the first study of its kind — normally patients receive two doses of the same vaccine — and will help determine the safety of mixing doses across different groups and with a variety of different time intervals.

The researchers said they wanted participants who were over 50 and had not yet been vaccinated to take part in the trial.

The 13-month study, known as "Com-Cov," is expected to first report initial findings in the summer. Its data could lead to a change in the U.K.'s vaccine policy.

In the U.S., the Centers for Disease Control and Prevention recently changed guidance for Covid-19 vaccines, saying that patients could mix the Moderna and Pfizer doses in "exceptional situations."

But the Pfizer and Moderna vaccines are both based on the same messenger RNA, or mRNA, platform. The U.K. trial, however, involves mixing vaccines based on different techniques. The AstraZeneca/Oxford vaccine uses an inactivated adenovirus, a type of virus that causes the common cold.

Trial participants will be tested to monitor their levels of antibodies and T cells, which search for and attack infected cells.

quote:

Originally posted by wtg:
The UK is trying some new approaches using existing vaccines.

quote:

As the world races to vaccinate and fight new variants of Covid-19, a new trial is trying something that could speed up the process: mixing shots.

Patients taking part in a clinical trial launched Thursday in the United Kingdom will receive different vaccines for their first and second doses: the vaccine developed by Oxford University and AstraZeneca, followed by the one from Pfizer and BioNTech, or vice versa.

The U.K.'s Department of Health said it was the first study of its kind — normally patients receive two doses of the same vaccine — and will help determine the safety of mixing doses across different groups and with a variety of different time intervals.

The researchers said they wanted participants who were over 50 and had not yet been vaccinated to take part in the trial.

The 13-month study, known as "Com-Cov," is expected to first report initial findings in the summer. Its data could lead to a change in the U.K.'s vaccine policy.

In the U.S., the Centers for Disease Control and Prevention recently changed guidance for Covid-19 vaccines, saying that patients could mix the Moderna and Pfizer doses in "exceptional situations."

But the Pfizer and Moderna vaccines are both based on the same messenger RNA, or mRNA, platform. The U.K. trial, however, involves mixing vaccines based on different techniques. The AstraZeneca/Oxford vaccine uses an inactivated adenovirus, a type of virus that causes the common cold.

Trial participants will be tested to monitor their levels of antibodies and T cells, which search for and attack infected cells.

https://www.nbcnews.com/news/w...cines-first-n1256683

quote:

The second dose of Pfizer Inc’s COVID-19 vaccine could be delayed in order to cover all priority groups as the first one is highly protective, two Canada-based researchers said in a letter published in the New England Journal of Medicine.

The vaccine had an efficacy of 92.6% after the first dose, Danuta Skowronski and Gaston De Serres said, based on an analysis of the documents submitted by the drugmaker to the U.S. Food and Drug Administration (FDA).

These findings were similar to the first-dose efficacy of 92.1% reported for Moderna Inc's mRNA-1273 vaccine, according to the letter here on Wednesday.

In its response, Pfizer said alternative dosing regimens of the vaccine had not been evaluated yet and that the decision resided with the health authorities.

Some countries, grappling with low supplies, are looking at dosing patterns or volumes that differ from how the vaccines were tested in clinical trials.

There are differences over the merits of such strategies, with some arguing the urgency of the pandemic requires flexibility, while others oppose abandoning data-driven approaches for the sake of expediency.

Skowronski and De Serres cautioned that there may be uncertainty about the duration of protection with a single dose, but said the administration of the second dose a month after the first provided “little added benefit in the short term”.

Skowronski works at the British Columbia Centre for Disease Control, while De Serres is from the Institut National de Santé Publique du Québec

quote:

Nearly 30 million people in the United States — and probably many others whose illnesses were never diagnosed — have been infected with the coronavirus so far. Should these people still be vaccinated?

Two new studies answer that question with an emphatic yes.

In fact, the research suggests that for these people, just one dose of the vaccine is enough to turbocharge their antibodies and destroy the coronavirus — and even some more infectious variants.

The results of these new studies are consistent with the findings of two others published over the past few weeks. Taken together, the research suggests that people who have had COVID-19 should be immunized — but a single dose of the vaccine may be enough.