Health authorities have launched an investigation after 14 people in Hong Kong were given expired Covid-19 vaccines at a private medical chain.

The Department of Health found after a routine check on Wednesday that BioNTech’s bivalent vaccines which had been kept between one to eight days after the suggested use by date were used on patients from March 21 to March 28 at the Kowloon Bay branch of Quality HealthCare.

Vaccine maker Fosun Pharma had suggested that the jabs should be kept at between two to eight degrees Celsius (35.6 to 46.4 degrees Fahrenheit) and be used inside 70 days after they were thawed out, the department said on Wednesday night.

The department added it had consulted city experts and the vaccine maker about the safety, efficacy and quality of the vaccine and said no re-vaccination was needed for the people affected.

An investigation is launched after a Hong Kong medical centre gave patients coronavirus shots past their “use by” dates.

But the authorities said Quality HealthCare should contact the affected patients to explain the situation and follow up on their health.

They said the clinic should deal with reports of discomfort immediately and also notify the department. No reports have been made.

Health officials said they would check to see if the medical centre had followed its guidelines.

“If there is any violation of the guidelines under the Covid-19 vaccination programme or the private clinic agreement, the Department of Health will handle it according to the established mechanism,” officials said.

Dr Leung Chi-chiu, a specialist in respiratory medicine, said the out-of-date vaccines would not be harmful as long as they had been kept in the correct temperature zone.

He added re-vaccination inside a short period might bring a greater risk of side effects such as myocarditis, an inflammation of the heart muscle.

Leung said the suggested use by date for vaccines was similar to the “best before” recommendations on food items and several days beyond the dates did not mean the jabs would be ineffective.

The department also announced that a section of window in a room at Tuen Mun Wu Hong Maternal and Child Health Centre had fallen from the second floor, but no one had been injured.

The piece of glass at the Wu Hong Street centre, which measured 0.5m by 0.8m (1.65 feet by 2.6 feet) fell onto an area near the car park at about 3pm on Wednesday as a staff member opened the window.

The department said it would ask the Architectural Services Department to carry out an inspection of windows at the health centre.

Safety in public healthcare buildings has been in the spotlight after a spate of incidents involving fallen items such as concrete slabs, false ceilings, and operating theatre lights.

Experts said the incidents should be a wake-up call for the government and public institutions to review maintenance schedules and the safety of buildings.