Thursday, August 5, 2021

No rush for booster shot to ward off Delta, say health experts

They say two doses provide adequate protection although a third shot can be considered for high-risk groups once the current immunisation programme is complete.

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Health experts say there is no need to rush into giving booster shots to ward off the more transmissible Delta strain amid concerns over the mutation which has been categorised as a variant of concern.

Yahya Mat Arip, a virologist at Universiti Sains Malaysia, said changes known as protein spikes occur which result in the effectiveness of antibodies.

“Say before this, antibody effectiveness was at 90%. With this mutation, it may decrease to 75%.

“A person would still have some level of protection, but third doses are recommended to provide the maximum protection,” he told MalaysiaNow.

According to the World Health Organization (WHO), the Delta variant has been reported in 96 countries so far and is expected to continue spreading.

Pfizer and BioNTech recently announced that they would seek regulatory authorisation for a third dose of their Covid-19 vaccine.

They cited data from an ongoing trial which showed that a third shot pushed antibody levels five to 10 times higher against the original coronavirus strain and the Beta variant, compared to the first two doses alone, saying a third dose was expected to perform similarly well against the Delta strain.

They are also developing a Delta-specific vaccine, clinical trials for which are expected to begin in August, subject to regulatory approvals.

Yahya said the present vaccine was based on the original virus first detected in Wuhan, while the vaccine to come would be based on the new variants.

He said protection of about 50% is achieved once a person has been given two doses of vaccine.

“There is no need for the government to rush to obtain vaccines for a third shot,” he said. “We need to focus on the first two doses, to provide protection for those with none.

“I am sure that the government is studying the matter and making early plans to order vaccines for a third dose.”

Azrul Mohd Khalib, chief executive of think tank Galen Centre for Health and Social Policy, said it was still too early to determine if a booster shot is needed.

“Data shows that the Pfizer and AstraZeneca vaccines are effective in fighting the Delta variant once a person has been fully inoculated,” he said, adding however that there is a lack of data on how other vaccines perform in this area.

Public health expert Dr Sanjay Rampal also cited data from a study in the UK which showed that the Pfizer and AstraZeneca jabs are 96% and 92% effective respectively at preventing hospitalisations due to the Delta strain once an individual has received both doses of vaccine.

He said a booster shot should only be considered once the current immunisation programme is complete.

“High-risk groups such as those over the age of 50 should be considered for booster distress,” he told MalaysiaNow.

Health director-general Dr Noor Hisham Abdullah previously pinpointed the Delta variant as one of the factors behind the spike in Covid-19 cases in the country.

He also said that the Delta strain is capable of causing infection within 15 seconds through airborne transmission.

Other factors identified by WHO as contributing to the spread of Covid-19 throughout the world include increased social movements which raise the number of close contacts, the inappropriate use of health resources, and the inequitable distribution of vaccines.

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