The Swiss manufacturer of Tamiflu has warned that a shortage of the medication being given to children ill with the flu will persist until June in Hong Kong due to an unexpected surge in demand following the end of the city’s mask mandate last month.

Roche, which produces the solution form of Tamiflu, on Saturday confirmed the drug shortage as paediatricians in the city warned that children with chronic illnesses could suffer serious complications if they were infected with both Covid-19 and Influenza A at the same time. One doctor said it was unclear how long the peak of the flu season would last this year given it began later than usual.

The drug manufacturer said there would be inadequate supply of the solution form of Tamiflu until June this year as demand had risen after Hong Kong ended its mask-wearing mandate on March 1. The confirmation came after some private doctors had said they had or would run out of the medication soon.

Roche has advised pharmacists to dissolve the contents of the pill version in water if necessary until stocks of the solution form are replenished.

Roche added it would work with the local health authorities to minimise the impact on medical workers and patients.

“We are taking all practicable steps to address the out-of-stock issue soon,” the company said.

It advised pharmacists and patients to dissolve the contents of the capsule version of the drug in water if necessary until the bottled solution became available again.

The pharmaceutical giant maintained that the supply of Tamiflu capsules had remained “very stable” in Hong Kong and other parts of the world, and it would continue to monitor demand for the drug.

William Chui Chui-ming, president of the Society of Hospital Pharmacists of Hong Kong, said the Tamiflu shortage was likely to be part of a wider global shortage.

Apart from young children, the Tamiflu solution was also being prescribed to elderly patients experiencing difficulty swallowing, he added.

While mixing a capsule’s contents with water was easy for residents to do at home, he advised the government to consider allowing the generic alternatives to Tamiflu produced by other drug makers.

According to health authorities, the city has a reserve of about 11 million doses of antiviral drugs, of which 90 per cent is oseltamivir, which is sold under the brand Tamiflu.

Before Roche’s statement, a health department spokeswoman said the government could provide the drug to the private sector to ensure a continuous supply during a shortage. But she added that authorities had learned from the local drug supplier that the product was still available in the market.

A Hospital Authority spokesman said it was closely monitoring flu cases and the stock of drugs, adding it had bought medication in a timely manner to ensure there was enough supply.

Dr Mike Kwan Yat-wah, from the University of Hong Kong’s department of paediatrics and adolescent medicine, said a surge in flu cases was expected after the city lifted its Covid-19 restrictions, citing a previous study that showed infections in Australia increased fivefold after the country axed its social-distancing curbs.

Dr Mike Kwan from the University of Hong Kong’s department of paediatrics and adolescent medicine.

He added that it was common to see children infected with different viruses at the same time.

“Parents should pay extra attention if children test positive for Covid-19 and influenza A, which we call a twindemic, or if they have Covid-19, the flu and the syncytial virus at the same time, referred to as a tripledemic, as they face a higher chance of serious complications,” Kwan said on a radio programme.

The paediatrician also warned that children who suffered from chronic diseases or had inherited poor immunity could face complications such as encephalitis, pneumonia and hepatitis if they were infected with multiple viruses at the same time.

According to the Department of Health, data indicated that the city had entered the flu season, with 77 per cent of the cases being influenza A (H1), which affects children and adults aged from 50 to 64 at a higher rate.

Hong Kong usually experiences two flu seasons every year, one between January and March or April, and between July and August. According to Kwan, the peak normally lasts for eight to 12 weeks in the winter season.

“But I cannot foresee how long the flu peak will last as it began late this year and we are celebrating the four-day Easter holiday with many leaving the city. We should keep a close eye on the development after the holiday ends,” he said.

Respiratory expert Dr Leung Chi-chiu said he expected the duration of the current peak flu season to be more or less the same as previous ones.

According to Leung, complications might not be caused by direct interaction between two to three viruses, but they were more likely among children with chronic illnesses.

“Coinfection is more likely to occur among those with underlying predisposing factors, such as suffering chronic diseases,” he said. “It is likely that the same underlying factors predispose them to more severe illness.”