SINGAPORE - People who have not been able to get vaccinated against Covid-19 owing to health reasons can be prescribed AstraZeneca's antibody drug to protect against the coronavirus.

In a statement on Monday (Aug 1), the Health Sciences Authority (HSA) said it has granted interim authorisation for the antibody drug cocktail called Evusheld, under the Pandemic Special Access Route.

Evusheld comprises two monoclonal antibodies and is administered by intramuscular injection, said HSA.

The two antibodies in the drug are derived from antibody-producing B-cells that were donated by recovering Covid-19 patients.

The treatment is authorised for adults who have not had a known recent exposure to a person with Covid-19 infection and are unlikely to mount an adequate immune response to Covid-19 vaccination due to a medical condition or are taking immunosuppressive medications or treatments or for whom Covid-19 vaccination is not recommended.

Examples of such people include those who are in an immunocompromised state from blood or bone marrow transplants or have human immunodeficiency virus (HIV) infections.

About 7 per cent of Singapore residents remain unvaccinated, according to the Health Ministry’s website.

Taking the Evusheld shot is not a substitute for vaccination in individuals for whom Covid-19 vaccination is recommended, said HSA.

"The treatment must be prescribed by a doctor and the suitability of use on the individual patient will require a careful clinical assessment by the prescribing doctor," it added.

Results from a clinical study in more than 5,000 participants found that there was a relative risk reduction of symptomatic Covid-19 illness by 77 per cent with Evusheld compared with a placebo.

The drug had protected them for about six months against Covid-19 variants, excluding Omicron.

At the time the study was conducted, the circulating variants of concern included Alpha, Beta, Gamma and Delta, said HSA.

Efficacy data for Evusheld was based on an ongoing Phase III study with participants aged 18 to 99, who had not been vaccinated against Covid-19 and had risk factors for an inadequate Covid-19 vaccination response or an increased risk for infection.

Said HSA: "Recent in-vitro data has shown that certain Omicron subvariants are less susceptible to Evusheld.

"Hence the duration of protection against the Omicron subvariants is currently unknown."

This means that more data is required to determine the drug cocktail's effectiveness against the currently circulating Omicron variant to further determine its continued benefits, HSA said.

It noted that the safety data showed that Evusheld was well-tolerated, and the incidence of adverse events reported in the clinical study was generally low.

Common adverse events reported were mild to moderate in severity, such as headache, throat pain, runny nose, nasal congestion and muscle pain, HSA added.

Said HSA: "While the study reported a higher incidence of cardiovascular adverse events with Evusheld, the causal relationship has not been established based on current available data.

"HSA will continue to closely monitor for any further cardiovascular safety signal."

The available clinical evidence has preliminary demonstrated that Evusheld is favourable for those who are unlikely to have an adequate immune response to Covid-19 vaccination or are not recommended to take the vaccine, HSA added.

As there was no clinical data in pregnant women, breastfeeding mothers and children, no recommendation could be made for these groups, it said.

As a condition for interim authorisation under the Pandemic Special Access Route, AstraZeneca is still required to collect and submit the relevant safety data from ongoing clinical studies to ensure the continued safety and efficacy of Evusheld, including its efficacy against prevailing variants, HSA said.

It added that interim authorisation may be terminated if new data suggests that benefits no longer outweigh the risks.

Under the Pandemic Special Access Route, HSA can start evaluating new vaccines, medicine and medical devices from the early stages of clinical studies, as and when real-time data is submitted by companies instead of waiting for the full data set to be submitted before starting its evaluation. 

To obtain full registration for Evusheld, the pharmaceutical and biotechnology company will need to submit the complete data set based on prevailing international standards, it added.