• Shares of Danish vaccine maker Bavarian Nordic jumped as much as 17% Thursday amid a wider rally for associated healthcare stocks.
• It comes after the World Health Organization declared an escalating mpox outbreak in Africa as a public health emergency.
• Medical tools supplier Precision System Science Co soared 40% in Tokyo and virus detection kit maker Shanghai ZJ Bio-Tech Co gained 8% in China.

LONDON — Shares of Danish vaccine maker Bavarian Nordic jumped as much as 17% Thursday amid a wider rally for associated healthcare stocks after the World Health Organization declared an escalating mpox outbreak in Africa as a public health emergency.

Bavarian Nordic, one of the only companies with an approved mpox vaccine, was 16.5% higher in early deals in Copenhagen, Denmark, extending 13% gains from the previous session when it said it said it could meet growing shot demand.

The stock pared gains to trade up around 8% by around 4:36 p.m. local time.

Shares of U.S. pharmaceutical company Emergent Biosolutions — whose ACAM2000 vaccine is one of two recommended by the Centers for Disease Control and Prevention (CDC) alongside Bavarian Nordic's JYNNEOS — climbed in after hours trade in New York.

Meanwhile, medical tools supplier Precision System Science Co soared 40% in Tokyo.

The WHO declaration on Wednesday — its second in two years for mpox — follows an outbreak of the viral infection in Democratic Republic of Congo that has spread to neighbouring countries.

The "public health emergency of international concern" status is the WHO's highest designation and aims to accelerate international public health measures and cooperation to contain a disease.

Mpox is a zoonotic disease that spreads from animals to humans, with flu-like symptoms and pus-filled lesions on the body. Usually mild, it can be fatal in rare cases.

The surge in cases is thought to derive from a new variant, known as clade Ib, which appears to spread more easily through close contact, including sexual contact. Cases of the new variant have since been confirmed in Burundi, Kenya, Rwanda and Uganda.

It comes after a prior outbreak of the virus in 2022, when thousands of cases were reported worldwide, prompting a WHO public health emergency declaration. That designation was removed in May 2023, following a steady decline in cases.

Brian Ferguson, associate professor of immunology at the University of Cambridge, said that the new outbreak was particularly concerning given its increased prevalence among children, and said more need to be done to improve vaccine access.

"Even though there are existing effective vaccines, there are not enough doses," and they are not getting to where they are needed, he said.

The WHO said it was working with countries and vaccine manufacturers to increase access for affected countries. The U.N. health agency said it has released $1.45 million in contingency funds and might need to release more in the coming days. It expects an immediate funding requirement of an initial $15 million will be needed for its response plan.

"The cost and availability of vaccine is going to be a great challenge," said Jimmy Whitworth, Emeritus professor at the London School of Hygiene and Tropical Medicine, adding that an estimated 10 million vaccine doses would be required to deal with the outbreak.

Bavarian Nordic CEO Paul Chaplin told the Financial Times that the company could ramp up vaccine supply to 2 million doses by the end of the year and 10 million by the end of 2025 if governments placed orders. "We have the capacity, but we need people to start placing orders pretty fast," he said.