SINGAPORE - The Covid-19 vaccine developed by Novavax has been approved for individuals here aged 18 and above, and is the first non-mRNA vaccine recommended as a booster dose by the Expert Committee on Covid-19 Vaccination (EC19V).

The Health Sciences Authority (HSA) said on Monday (Feb 14) that it had granted interim authorisation for Novavax's vaccine - manufactured under the name Nuvaxovid - on Feb 3 under the Pandemic Special Access Route (PSAR).

The vaccination regimen comprises two 5mcg doses of Nuvaxovid to be administered three weeks apart.

The first batch of Nuvaxovid is expected to arrive in Singapore in the next few months.

The expert committee said Nuvaxovid is an acceptable alternative to the mRNA vaccines for booster jabs for those aged 18 and above. One dose is recommended as a booster dose about five months after the last dose of the primary series vaccination, it said in a statement on Monday. 

HSA said it has reviewed that the vaccine meets quality, safety and efficacy standards, and that its benefits outweigh the risks for the Singapore population.

Two groups of experts from HSA's Medicines Advisory Committee and Panel of Infectious Diseases Experts were also consulted, and they agreed with HSA's recommendation for PSAR authorisation.

HSA said its review was based on two phase 3 clinical studies conducted in the United States, Mexico and Britain, comprising more than 40,000 trial participants aged between 18 and 95.

The results showed that Nuvaxovid demonstrated a vaccine efficacy of about 90 per cent against symptomatic Covid-19 and 100 per cent in preventing severe Covid-19.

The vaccine showed consistent efficacy against the Alpha variant, but there was no data on the Delta and Omicron strains, as these variants were not prevalent at the time Novavax conducted the clinical trials, HSA added.

In a statement, the multi-ministry task force handling the pandemic said it has accepted the recommendation from the EC19V to include the Novavax vaccine in the national vaccination programme.

The vaccine will be rolled out free to those eligible when shipments arrive.

The EC19V said there have been no significant safety concerns with Nuvaxovid. Most side effects were mild to moderate in severity and resolved in one to three days, including injection site pain, fatigue, headache and muscle aches.

The expert committee also noted that using Nuvaxovid as a booster jab resulted in a substantial rise in antibody levels, although to a lower extent compared with boosting with mRNA vaccines. These were the findings from a randomised, controlled, phase 2 trial in Britain with more than 2,800 participants that studied various vaccines for booster jabs. 

While the EC19V recommended Nuvaxovid as an acceptable alternative to mRNA vaccines, it said that those remain the preferred choice due to their higher efficacy and the stronger immune response they generate. 

The committee also said that Nuvaxovid is preferred to China's Sinovac vaccine for those medically ineligible to receive the mRNA jabs. This is due to Sinovac's lower efficacy.

"Sinovac-CoronaVac vaccine should only be used by persons who are medically ineligible for the mRNA vaccines and Nuvaxovid," the committee said.

"The availability of Nuvaxovid will offer persons medically ineligible for the mRNA vaccines a good alternative to achieve vaccine protection against Covid-19. The committee encourages all eligible persons to be vaccinated and boosted at the earliest opportunity." 

HSA noted that as with all vaccines, there will be a small proportion of people who may experience severe side effects, like those with a history of anaphylaxis (rapid onset of severe allergic reactions). In such cases, immediate medical attention should be sought. 

Such people should not take a second dose of the vaccine, HSA said.

It added that it cannot recommend whether the vaccine can be used for those aged under 18 or who are severely immunocompromised, as safety and efficacy data is not available yet.

Novavax has to monitor the long-term efficacy of its vaccine, as well as monitor its safety to determine whether it is safe for pregnant women, children and those who are immunocompromised.

Q: How does Nuvaxovid work?

A: Nuvaxovid is a protein-based, or protein-subunit, vaccine. It is not an mRNA vaccine, such as the Pfizer-BioNTech/Comirnaty and Moderna jabs.

Vaccines based on mRNA technology use material from the virus to teach the body's cells to make copies of a protein unique to the virus, and in this manner build up resistance to it.

On the other hand, protein-based vaccines include pieces of the virus. When a person is vaccinated with them, their body realises that the protein should not be there and creates antibodies to fight it.

Nuvaxovid teaches the body's immune system to create antibodies that fight the coronavirus' spike protein, which the virus uses to enter human cells.

In order to make the protein, scientists took a modified spike gene and put it into an insect virus.

The virus was allowed to infect moth cells and, when it did, the infected cells created many spike proteins.

These spike proteins were then harvested, purified and put into nanoparticles. These particles were combined with an extract from the soapbark tree, which helps boost the immune system's response.

When the vaccine is injected into a person, the body's immune system will encounter the nanoparticles and in doing so, learn how to fight the virus.

Q: What are some other protein-based vaccines? Is this a new method of developing a vaccine?

A: Protein-based vaccines are considered a conventional approach to vaccines, and long-established vaccines against whooping cough and shingles, for instance, employ this approach.