Mass vaccination against monkeypox not recommended by MOH after WHO declares it a global health emergency

SINGAPORE: The Ministry of Health (MOH) does not recommend the mass vaccination of Singapore’s population against monkeypox, Health Minister Ong Ye Kung said on Monday (Jul 25), reiterating the ministry’s stance on the viral disease.

This comes after the World Health Organization (WHO) on Saturday declared the monkeypox outbreak a public health emergency of international concern.

“As of now, given the self-limiting nature of the disease, MOH does not recommend the mass vaccination of the whole population against monkeypox, because the benefits do not outweigh the risk,” Mr Ong said in a Facebook post.

“We will continue to monitor the situation closely.”

In Singapore, four imported and four local cases of monkeypox have been detected.

"There was no evidence of them transmitting the infection to other people in the community,” he said.

“MOH also quarantines their close contacts for up to 21 days since last exposure, while lower risk contacts are monitored through phone surveillance."

Each monkeypox case typically generates three to four close contacts who require quarantine. This is unlike COVID-19, which may generate up to 20 quarantine orders, said the Health Minister.

Singapore's seventh and eighth monkeypox cases both tested positive on Jul 24.

One of them is an imported case involving a 46-year-old Estonian man who came to Singapore from London on Jul 21 and sought medical care on Jul 23 after developing symptoms.

The other is a 26-year-old Singaporean man who developed rashes and sought medical attention on Jul 24. 

A surge in monkeypox infections has been reported globally since early May outside the West and Central African countries where the disease has long been endemic.

A public health emergency of international concern is the top alert available to the WHO to tackle a global disease outbreak.

It is defined as "an extraordinary event which is determined to constitute a public health risk to other states through the international spread of disease and to potentially require a coordinated international response".

According to the United States Centers for Disease Control and Prevention (CDC), smallpox vaccines can protect people from getting monkeypox because the viruses that cause the diseases are closely related.

The Jynneos and ACAM2000 smallpox vaccines are currently being used in the US, and while past data has shown smallpox vaccines to be up to 85 per cent effective against monkeypox, they can have serious side effects.

The US Food and Drug Administration (FDA) said ACAM2000 can cause myocarditis and pericarditis. Those who have recently received the vaccine can also infect unvaccinated people with the vaccine virus if they have close contact.

As for the Jynneos vaccine, adverse reactions may include muscle pain, headache, fatigue, nausea and chills.

In a written reply to Parliament on Jul 4, Mr Ong explained why MOH is not recommending monkeypox vaccinations for the general population.

“Unlike COVID-19 vaccination, mass population-wide vaccination with the smallpox vaccine is not recommended as a preventive strategy for monkeypox, in line with international recommendations and the global response thus far,” he wrote.

“Although the smallpox vaccine is up to 85 per cent effective at preventing monkeypox, it has potentially severe side effects.

“For the general population, the risks of complications outweigh the benefits, because they are at low risk of being infected.

“Exercising personal responsibility to avoid high-risk activities, especially when symptomatic, and practising good personal hygiene remain effective at reducing the risk of transmission in the general population.”

According to MOH, the transmission of the disease occurs when a person comes into close contact with the monkeypox virus through an infected animal, infected person or contaminated environment.

“Animal-to-human transmission may occur by a bite or scratch from an infected animal, bush meat preparation, or direct contact with the blood, body fluids, or skin or mucosal lesions of infected animals,” the ministry says on its website.

“Human-to-human transmission can occur via exposure to respiratory droplets or direct physical contact with the blood, body fluid or lesion material from (an) infected individual or contaminated material.”