The Pirbright Institute, in collaboration with the University of Oxford, announced Tuesday that two doses of an experimental COVID-19 vaccine successfully produced a greater antibody response than a single dose in pigs.
The Surrey, England institute published research showing that two doses of the ChAdOx1 nCoV-19 vaccine (AZD1222) revealed a “marked increase in neutralizing antibodies,” which bind to the virus to block infection.
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The same investigational vaccine previously protected six monkeys from pneumonia caused by the virus. According to the Oxford researchers, the ChAdOx1 nCoV-19 vaccine is made from the ChAdOx1 virus, a weakened version of the common cold that has been genetically engineered to make it impossible for it to replicate in humans.
It is not yet known what level of immune response will be required to protect humans against SARS-CoV-2, according to a statement from the Pirbright Institute.
Human vaccine trials are underway, and the research is said to offer important findings because it reveals that two doses of the new vaccine may offer more protection than one dose.
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“These results seem encouraging, as giving two injections with the same vaccine increases antibody responses that can neutralize the virus, but what matters is the response in humans,” said Bryan Charleston, professor and director of the Pirbright Institute.
Charleston said the pig proved to be a valuable model for testing human vaccines due to greater physiological similarities (such as body weight and metabolic rate) compared to other animals.
ChAdOx1 nCoV-19 also demonstrated T-cell responses, which the study’s lead author, Professor Simon Graham, called “very encouraging.”
“A combination of these responses is likely to work in synergy to prevent and control infection, as we and others have recently demonstrated in the context of experimental influenza vaccines,” said Graham.
The news comes after Barry Bloom, an immunologist and professor of public health at the TH Harvard TH Chan School of Public Health in Boston, told USA Today earlier this month that nearly all vaccine developers are considering two injections in their regimes.
According to the media report, the first shot in the series “would prime the immune system” to help the body recognize the virus, followed by a second shot to “strengthen the immune response.”
After the first dose of a vaccine, the immune system develops antibodies and immune cells in about 14 days, says LJ Tan, director of strategy for the Immunization Action Coalition and co-chair of the National Summit on Adult Immunization and the National Summit of Influenza Vaccines.
While at this point it is unclear exactly how long the antibodies could offer immunity against COVID-19, researchers at St. George’s University in London said that pathogen neutralizers may remain stable in the blood of an infected person for two months after diagnosis.
James Rogers and Christopher Carbone of Fox News contributed to this report.