PETALING JAYA: Reducing the dosing interval for AstraZeneca vaccines is needed to protect Malaysians better, health experts say, especially with variants posing a risk to the country’s mass vaccination programme.

       Universiti Malaya epidemiologist Prof Datuk Dr Awang Bulgiba Awang Mahmud said shortening the dose interval may be needed due to the global prevalence of the Delta variant which threatens to undermine the countries’ road to recovery.

       “At first, enabling maximum coverage of the population was used as a rationale for longer dose intervals in the UK to get the maximum number of people with at least some protection afforded by a single dose.

       “However, the new Delta variant (B.1.617.2) may prove to be a tougher variant to combat, and may require that the second dose be given sooner rather than later as a single dose.

       “We do not know what the prevailing variant in Malaysia is right now as we do not do enough genomic surveillance, but it is likely that the Delta variant will displace the local variants if it takes root.

       “Experience in the UK suggests that two doses, instead of one, would be effective in preventing hospitalisation and death against the Delta variant,” he said.

       Universiti Malaya Department of Social and Preventive Medicine Faculty of Medicine’s Prof Dr Moy Foong Ming also said the AstraZeneca vaccine was more effective when two doses were given than just one. She added that the jab was only 30% effective against symptomatic Covid-19 caused by the Delta variant three weeks after the first dose, and this would be boosted to between 60% and 80% two weeks after the second dose.

       As such, she said there are benefits for shortening the dosing interval, especially following the emergence of the Delta variant.

       However, she said that as the delivery of vaccine supplies is still an issue, it may be better to only allow shortened dosing intervals for certain groups.

       “The shortening of dosing intervals can be applied to senior citizens and individuals with comorbidities.

       “If there is a shortage of supply, those aged less than 60 years old without comorbidities can have their second doses at the usual dose interval,” she said.

       Malaysian Society of Allergy and Immunology president Prof Dr Baharudin Abdullah, however, pointed out that the vaccine’s efficacy rates would be impacted by a change in the dosing interval.

       He said research showed that the efficacy rate of the AstraZeneca vaccine was 81% in a 12-week interval, compared with 55% in a six-week interval.

       “On receiving the vaccines, the human body produces antibodies and other cells responsible in fighting against the infection.

       “Typically, it takes a few weeks for the body to produce sufficient amounts of such factors,” he said.

       “Therefore, when a second dose is given too close to the first dose, the interval may not be enough for the human body to produce them at a satisfactory level.”

       The research, which involves over 17,000 participants, was published in The Lancet medical journal in March.

       He added that the 12-week gap was employed as it could afford protection to more people in the shortest time possible to prevent transmission.

       “However, in the UK, there is a recent push for an eight-week interval as the majority of people have received their vaccination and the accelerated schedule can make it quicker for them to get their citizens fully vaccinated.

       “In Canada, the eight-week interval was proposed to address the highly infectious Delta variant, but the dosing interval is based on individual circumstances.

       “For those who travel frequently or carry out any high-risk activities, it is advisable for the second dose to be given sooner,” he said.