KUALA LUMPUR: The emergence of more aggressive new variants has sparked questions about the effectiveness of existing Covid-19 vaccines against them.
Even the World Health Organisation has urged pharmaceutical companies to ensure that the vaccines produced by them are modified to address the newer and more infectious variants.
In Malaysia, the issue of vaccine efficacy cropped up after the government announced earlier this month that it will stop using the Covid-19 vaccine produced by China’s Sinovac Biotech Ltd.
Commenting on the vaccine efficacy matter, Dr Nurul Yuziana Mohd Yusof, a senior lecturer from the environmental health cluster at Universiti Kebangsaan Malaysia’s Department of Earth Science and Environment, said the vaccines produced by Sinovac, Pfizer Inc and AstraZeneca Plc have proven to be effective in preventing severe infections in Covid-19 confirmed cases.
She said studies have shown that the vaccines concerned can protect individuals against infections by SARS-CoV-2, the coronavirus that causes Covid-19.
On the differences among the Pfizer, AstraZeneca and Sinovac vaccines, Dr Nurul Yuziana said the Pfizer and AstraZeneca vaccines produce specific antibodies for the virus’ spike protein, while Sinovac generates antibodies to act against the entire structure of the virus, including its spike protein.
“The spike protein acts as if it holds the key for the Covid-19 virus to enter the cells (of the body) through the ACE-2 receptor. Antibodies targeting or sticking to the spike protein will prevent the SARS-CoV2 from entering the cells of the body. The antibodies will also neutralise the virus and in this state, the virus cannot enter the cells and multiply,” she explained.
On the effectiveness of the three vaccines against the new Covid-19 variants, Dr Nurul Yuziana said various studies have shown that two doses of the Pfizer and AstraZeneca vaccines have an efficacy of more than 50 percent against the new variants.
“In a study published by the New England Journal of Medicine recently, Pfizer was shown to have an efficacy of up 93.7 percent against the Alpha variant and 88 percent against Delta, while for AstraZeneca, it was 74.5 percent (Alpha) and 67 percent (Delta).
“As for Sinovac, to date, there has been no scientific data to evaluate its efficacy against the new variants... most likely, it is still under study or analysis,” she added.
Dr Nurul Yuziana also stressed that the effectiveness of any vaccine can only be ascertained through comprehensive analysis encompassing various data, including the vaccination status of a population.
“Apart from that, we also have to conduct lab tests to get a more detailed analysis of the variant type, compared to existing Covid-19 screening methods such as the multiplex RT-PCR (Real-Time Reverse Transcription-Polymerase Chain Reaction) method and DNA sequencing to analyse information on genetic changes or virus mutations.
On July 23, Sinovac Biotech Ltd spokesman Liu Peicheng said the company’s CoronaVac (also known as Sinovac) vaccine was effective in fighting the Delta variant, which currently is the most aggressive Covid-19 variant and has the highest transmissibility rate.
He said although no data is available yet on its protective effect, studies have proven the vaccine’s efficacy in countries such as Brazil, Indonesia, Chile and Turkey, where CoronaVac has been widely used.
One of the most widely used Covid-19 vaccines worldwide, CoronaVac is an inactivated vaccine that works by using killed viral particles to expose the body’s immune system to the virus without risking a serious disease response. -Bernama
