Researchers from the United Kingdom recently launched a study that would mix and match two different vaccines against COVID-19 in a bid to alleviate the frightening logistics of immunizing millions and possibly boost immune responses in the process.
A report from Nature indicates that most COVID-19 vaccines are provided as two injections: one as an "initial 'prime' dose, and the other, a follow-up 'boost' for the stimulation of memory cells of the immune system and amplification of immune response.
The clinical test is designed to test the immune responses participants to getting a shot of COVID-19 which Oxford and pharmaceutical firm AstraZeneca produce, using a harmless virus to carry a key gene of the coronavirus into cells. The other shot of the vaccine is produced by Pfizer, a drug company, using RNA instructions to activate an immune response.
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Oxford earlier said it would trial combinations as well, of its COVID-19 vaccine with Sputnik V, the Russian COVID-19 vaccine which uses harmless viruses to transport elements of the coronavirus into cells.
Two Vaccines Combined
Developers of vaccines usually combine two vaccines to fight the same pathogen, and the study investigators are keen to apply the same strategy of having two vaccines combined. Such a method is identified as heterologous prime-boost that will combat COVID-19.
According to Dan Barouch, director of Boston, Massachusetts-based Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, last year, a heterologous prime-boost combination was approved by European regulators as a protection from Ebola virus, and investigational HIV vaccines frequently depend on the strategy
However, it has yet to be tried using vaccines as protection from COVID-19, which are usually administered as a repeat jab of the same vaccine.
Mix-and-Match Vaccines
As indicated in the said study, the ability to mix-and-match vaccines could turn vaccination programs into more flexible ones that would make the process speedier and lessen the impact of any disruptions in the supply chain.
Mary Ramsay, head of immunization at Public Health England said at a press briefing, it's really making "the implementation much simpler."
Oxford earlier said it would trial combinations as well, of its COVID-19 vaccine with Sputnik V, the Russian COVID-19 vaccine which uses harmless viruses to transport elements of the coronavirus into cells.
Sputnik, which was shown this week, to have more than 90-percent efficacy against COVID-19, is reportedly a heterologous prime-boost vaccine itself, that consists of different viral components in both the first and second doses.
Two-Dose Schedules
Some scientists also think that combination of two vaccines could boost immune responses by binding the best features of each.
That would be specifically desirable at present, Barouch said, adding that developers of COVID-19 vaccines are fighting against COVID-19 strains that appear to be partly resistant to specific immune response.
It is possible that responses might be better compared to what either vaccine can attain on its own. The expert also explained that remains to be proven experimentally for COVID-19.
This Oxford trial is aiming to sign up around 820 individuals, and it will trial two dosing schedules: one with a four-week interval between the two jabs, and another that has a 12-week interval.
Focus on T Cells
The study investigators explained, "the trial will not look directly at how well the combination shields" against the virus. Such a study should be much more extensive and would take long for completion.
Rather, the research group will take regular samples of blood to gauge levels of antibodies and immune cells also known as T cells that participants produce to combat COVID-19. The team will closely monitor as well, for safety concerns.
T cells could be key to strengthening immune response. More so, RNA vaccines have produced powerful antibody responses to COVID-19.
However, they have not proven to be as good and effective as the AstraZeneca and Oxford vaccine when it comes to stimulating a class of T cells identified as CD8+ T cells, explained immunologist Zhou Xing from the Hamilton, Canda-based McMaster University.
This cells, according to research boosts an immune response by determining and killing cells infected with the COVID-19 virus.
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