MORE studies are needed to determine whether vaccines should be administered to those who have recovered from Covid-19, said director-general of health Dr Noor Hisham Abdullah.

“There are already some discussions on this. We probably need some studies to determine it,” he told The Malaysian Insight.

Noor Hisham said those who receive two doses of the vaccine will develop a strong immune response against the virus due to the high volume of protective antibodies present in the system.

Therefore, longitudinal studies – which look into the volume of antibodies in a recovered patient and the duration they can last – will be required, he said.

“Only based on this can we decide whether those recovered from Covid-19 need any vaccination,” he said.

“Having said that, there are some suggestions to provide a single dose vaccine to those who have recovered from Covid-19 to give them a ‘boost’ to prime the immune system again.”

The Health Ministry said previously the Covid-19 vaccine developed by the Institute of Medical Biology, Chinese Academy of Medical Sciences – which is currently used in Malaysia’s first clinical trial – won’t be administered to former patients.

France became the first country to recommend a strategy to vaccinate recovered patients.

Its public health authority said last week that it plans to vaccinate recovered patients with one dose of the coronavirus vaccine instead of the usual two.

Those previously infected by the virus would have developed an immune response similar to that produced by a vaccine dose, therefore a single dose after infection would likely suffice, it said.

The World Health Organisation said last week preliminary reports from South Africa show that former Covid-19 patients had been reinfected by a more contagious variant of the coronavirus.

When asked to comment on this, Noor Hisham said there were also several reports of reinfection, including a recent case in Singapore.

In Malaysia, there was one case in Sabah that was a possible reinfection.

However, health authorities are unable to characterise the virus as they could only sequence the virus from the second infection because the first was inadequate, he said.

“Reinfection is possible if the person who was infected during the first time did not mount sufficient immune response, thereby not able to provide sufficient neutralising antibodies the second time around, thus getting reinfected,” Noor Hisham said.

Viruses are constantly undergoing mutation, therefore, there is a possibility of reinfection, he added.

To prove reinfection, viral characterisation through full genome sequencing must be conducted during both infections. This is to prove that there were two distinct viruses present in the system.

However, there must be a sufficient period of no symptoms between both infections – to show that the person has fully recovered from the first infection and was free from any symptom until the second infection.

Malaysia is set to receive its first batch of the vaccines from Pfizer-BioNTech at the end of this month. This will be followed by China’s Sinovac.

Putrajaya has also inked procurement deals with UK’s AstraZeneca, Russia’s Sputnik V and China’s CanSino.

The government is looking to vaccinate around 26.6 million people within the first 12 months. – February 16, 2021.