The COVID-19 vaccine developed by the University of Oxford and AstraZeneca is up to 90% effective, a new study has found. Pool Photo by Saul Loeb/UPI | License Photo
Dec. 8 (UPI) -- The Oxford COVID-19 vaccine protects 70% of those who receive it from infection, a study published Tuesday by the Lancet found.
The vaccine, developed in conjunction with drugmaker AstraZeneca, prevents infection in 62% of people who receive two full doses and in 90% of those given a half dose followed by a full dose, the data showed.
The study results include two dosing regimens because some participants early in the trial mistakenly received a half-dose.
Health agencies deemed this to be safe and allowed the trial to continue, with these participants then receiving a full dose -- with this group showing the highest vaccine efficacy in the trial.
In addition, the two-dose shot was found to be safe, with only three out of 23,745 participants experiencing serious side effects, the researchers said.
All three vaccine recipients who experienced side effects have recovered or are recovering, and remain in the clinical trial, according to the researchers.
"Control of the pandemic will only be achieved if the licensing, manufacturing and distribution of these vaccines can be achieved at an unprecedented scale and vaccination is rolled out to those who are vulnerable," study co-author Andrew Pollard said in a statement.
"Our findings indicate that our vaccine's efficacy exceeds the thresholds set by health authorities and may have a potential public health impact," said Pollard, a professor at the University of Oxford in England.
The Oxford COVID-19 vaccine uses a chimpanzee adenovirus that cannot cause disease in humans that carries the coronavirus spike protein, which is how COVID-19 infects cells.
Once the spike protein's genetic code has made it into vaccinated people's cells, it effectively teaches the immune system to recognize and attack the virus, according to Pollard and his colleagues.
The United States has provided at least some of the funding for the Oxford trials, with the promise that as many as 300 million doses -- enough to inoculate 150 million people -- will be provided.
In this study, half of the participants were given the COVID-19 vaccine and the other half given a control -- either a meningococcal conjugate vaccine or saline solution -- the researchers said.
Participants in the COVID-19 vaccine group received two doses each, according to the researchers.
In addition, 1,367 of the study participants received a half dose as their first dose, followed by a full second dose, the researchers said.
Of the 23,745 participants, 168 experienced a total of 175 severe side effects, but 172 of them were unrelated to the COVID-19 or control vaccines, according to the researchers.
Fourteen days after they received the second dose, 30 study participants who received the COVID-19 vaccine developed symptomatic infection, compared with 101 in the control group, for a 70% effectiveness rate, the data showed.
However, three of the 1,367 participants who received the low-dose/standard-dose vaccine developed symptomatic COVID-19 infection, the researchers said.
All 10 participants who developed severe COVID-19 during the three-month observation period had received the control vaccine, according to the researchers.
"Here we have shown for the first time that an adenoviral vectored vaccine -- a type of vaccine technology which has been in use since 2009 -- is efficacious and could contribute to disease control in the COVID-19 pandemic," co-author Sarah Gilbert, a professor at the University of Oxford, said in a statement.