CORONAVIRUS/New study shows higher efficacy of AstraZeneca in mix-and-match with Medigen

12/04/2021 08:01 PM
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Chang Gung Hospital workers receive their first dose of the COVID-19 vaccine when Taiwan began rollout it vaccination program on March 22. CNA file photo
Chang Gung Hospital workers receive their first dose of the COVID-19 vaccine when Taiwan began rollout it vaccination program on March 22. CNA file photo

Taipei, Dec. 4 (CNA) A recent COVID-19 vaccine trial carried out in Taiwan has found that a mix of AstraZenca and the locally developed Medigen is more effective than two doses AstraZeneca, the head of the research team said Saturday.

The trial, initiated by Chang Gung Memorial Hospital (CGMH), was conducted among 100 people aged 22-62, who were divided into two groups, with one group given two doses of the AstraZeneca vaccine, and the other a mix-and-match of AstraZeneca and Medigen, said the team leader Chen Chih-jung (陳志榮).

In the mix-and-match group, the neutralizing antibody geometric mean titers (GMTs) after 10 days were 1.8 times higher than among those who received two doses of AstraZeneca, said Chen, who heads the Molecular Infectious Diseases Research Center at the hospital's Linkou branch.

After 28 days, the level of neutralizing antibodies against COVID-19 was 1.1 times higher in the mix-and-match group than in the AztraZeneca group, he said, during the release of the trial findings at a seminar at the hospital.

The study also found that the GMTs were twice as high when the Medigen shot was given four to six weeks after the AstraZenca, compared with an eight- to 10-week interval, Chen said.

More AstraZeneca doses have been administered than have been officially received because medical workers can sometimes get more than the standard number of shots from a vial.
More AstraZeneca doses have been administered than have been officially received because medical workers can sometimes get more than the standard number of shots from a vial.

In another study at the hospital, the Moderna vaccine was found to be much more effective than AstraZeneca, he said, adding that the level of neutralizing antibodies produced by both vaccines after two doses was tracked among 683 CGMH employees.

In a mix-and-match group, the level of antibodies against COVID-19 was far from ideal when a Moderna shot was given more than 12 weeks after a first dose of AstraZena, Chen said.

People who decide on mix-and-match, therefore, are advised to take the second shot no more than 10 weeks after the first one, he said.

In the case of the CGMH employees, Chen said, their second shots were delayed for more than 12 weeks because of Taiwan's supply issues after its launched its COVID-19 vaccination program on March 22, and hospital workers were allowed to mix-and-match.

Currently, Taiwan allows people who received the AstraZeneca vaccine as a first dose to be given either Pfizer-BioNTech or Moderna as their second shots, with a minimum interval of eight weeks.

To date, 59.73 percent of Taiwan's 23.41 million population is fully vaccinated, having received two shots of a COVID-19 vaccine, while 78.12 percent has received at least one dose, according to government data.

(By Chang Ming-hsuan and Kay Liu)

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