Medical deans back mixed-jab strategy against Delta contagion
Deans of Faculties of Medicine at 10 universities backed a mix-and-match vaccine strategy to combat the fast-spreading Delta variant on Wednesday.
The deans, who are also advisers to the Centre for Covid-19 Situation Administration (CCSA), issued a statement supporting the National Communicable Disease Committee’s proposal for a first jab of Sinovac followed by a second of AstraZeneca to increase immunity against fast-spreading variants of Covid-19.
The deans cited the rapid increase of Delta infections in Thailand, which logged 9,186 new Covid-19 cases on Thursday with 98 deaths.
“In Bangkok alone, up to 69 per cent of patients have the Delta variant, which has a higher mortality rate than other variants,” said their statement. “Also, the Delta variant tends to be less responsive to vaccines, which have been developed based on other variants.”
The statement added that one jab of AstraZeneca or two jabs of Sinovac produced a low level of neutralising antibodies – not enough to protect against Delta infection.
However, two studies show that mixing and matching doses boosts immunity, it said.
“A Chulalongkorn University study of 36 volunteers and a Department of Medical Sciences study of 18 volunteers showed that a Sinovac jab followed by an AstraZeneca jab boosted their immunity up to eight times more than people who received two jabs of Sinovac,” said the statement.
The volunteers’ immunity also rose at a faster rate than those who received two jabs of the same vaccine, it added. “People who receive two jabs of AstraZeneca will achieve the desired level of immunity against Delta variant eight weeks after the first jab is given, while those who receive Sinovac and then AstraZeneca jabs can achieve the same immunity level in only 5-6 weeks.”
The deans also said 1,102 people had received two different vaccine brands after shortages of Sinovac for their second dose meant they had to get an AstraZeneca jab instead.
“We have studied people in this group closely and found that none of them developed severe allergic reactions or died after getting the jabs. Most importantly, none were infected with Covid-19.”
The deans also supported giving booster shots (third jabs) to front-line medical staff as protection against Delta. “Medics given two jabs of Sinovac should get another jab of AstraZeneca or any mRNA type vaccine at least four weeks after the second jab to reduce the infection risk from treating patients,” the deans said.
