Falling child vaccination rates raise concern as Hong Kong flu deaths rise

Hong Kong officials are warning about influenza because several risks are occurring together. The current season began in June and has not eased, even though flu seasons traditionally peaked in winter. Vaccination has also declined, leaving more people vulnerable to infection and serious illness.

The concern became sharper after a 12-year-old unvaccinated girl died from influenza A. She developed fever, cough, diarrhoea and vomiting, then suffered cardiac arrest and multiple organ failure. In August, a seven-year-old boy also died during the same flu season.

Centre for Health Protection controller Edwin Tsui Lok-kin said the season may last longer than last year. He also noted that vaccination among children aged two to 11 was about five percentage points lower than last year. Authorities are studying whether post-pandemic changes in virus transmission are contributing to the unusual pattern.

Influenza A is a type of influenza virus that infects the respiratory system. Most infections cause symptoms such as fever and cough, but illness can become life-threatening when the infection or the body's response disrupts vital organs. Risk can be higher for people with underlying health conditions, although severe outcomes can also occur in previously healthy children.

The 12-year-old girl in Hong Kong had influenza A complicated by septic shock, disseminated intravascular coagulation and multi-organ failure. She suffered cardiac arrest and was resuscitated. A seven-year-old boy died earlier after influenza A(H3) infection, with shock and encephalopathy, a serious brain complication.

These cases show why influenza is not always a mild illness. The article does not establish that influenza A caused every complication through one single pathway. It does show that infection can coincide with shock, circulation problems, brain injury and failure of several organs.

Vaccination among children in nursery, kindergarten or primary school, including those aged two to 11, is about five percentage points lower than last year. That decline matters because children are a large part of school and family networks, where influenza can spread readily. Lower coverage may leave more children susceptible during a prolonged season.

Since September 17, Hong Kong has administered more than 900,000 flu vaccine doses. During the same period last year, authorities had given one million doses. Centre for Health Protection controller Edwin Tsui Lok-kin described the difference as a slight decrease of about 10 per cent.

The figures describe doses given, not necessarily the exact percentage of the whole population vaccinated. They also cover all reported doses, while the five-point decline refers specifically to children. Officials are particularly concerned about this child vaccination gap as the season continues.

When fewer children receive influenza vaccines, a larger share may be susceptible to infection. This matters especially in nurseries, kindergartens and primary schools, where children spend time together. More infections can also expose family members and other vulnerable people, although the article does not quantify how much transmission rises.

Hong Kong's vaccination rate among children aged two to 11 is about five percentage points lower than last year. During the current season, a 12-year-old unvaccinated girl died after influenza A led to septic shock, disseminated intravascular coagulation and multi-organ failure. A seven-year-old boy also died in August, though he had received the seasonal vaccine.

Vaccination cannot prevent every infection or guarantee a mild illness. However, lower coverage removes some protection at population level while the season persists. Officials are therefore watching child vaccination rates closely and warning that continued spread could bring further severe cases.

Hong Kong's continuing summer flu season is unusual because influenza traditionally followed a winter pattern. Summer outbreaks did happen in the past, but only in about half of the previous 10 years. The current season began in June and has continued into roughly week 16 without clear signs of decline.

The unusual pattern is not limited to one year. Hong Kong experienced a summer flu season last year and has experienced another this year. Centre for Health Protection controller Edwin Tsui Lok-kin said authorities were monitoring possible changes in how the virus spreads after these two consecutive summer seasons.

Officials do not yet have enough scientific data to explain the shift. Tsui said changes in influenza transmission patterns after the Covid-19 pandemic need further examination. For now, the prolonged season means Hong Kong cannot rely on the usual expectation that influenza will be largely over after winter.

Influenza viruses change over time, and different strains can behave differently in a population. A strain that spreads more easily, reaches people with less existing protection, or remains active under different conditions could help extend a season. The article links the longer season to a strain shift, but does not identify the exact strain responsible.

Last year, Hong Kong's flu season was mostly over by week 18. This year, officials were around week 16 with no sign of weakening, and the season had already continued since June. Edwin Tsui Lok-kin attributed the difference to a change in the virus strain.

Strain changes can also affect how well existing immunity or vaccines match the circulating virus, although the article does not provide a vaccine-match assessment. Authorities are collecting more scientific data because summer flu seasons have now occurred consecutively. That evidence will help clarify whether transmission patterns have genuinely changed.

Flu vaccination and community coverage work together in two ways. A vaccinated person has protection against influenza, lowering the chance of infection or severe illness. When many people are vaccinated, the virus has fewer susceptible people to infect, which can reduce opportunities for spread and help protect people who remain vulnerable.

Hong Kong's child vaccination rate is about five percentage points lower than last year, while more than 900,000 doses have been given since September 17. Officials are concerned because the season has continued through summer. The two child deaths show that severe illness can still occur, although one of those children had received the seasonal vaccine.

Vaccines are not perfect, and community protection does not eliminate influenza. It can, however, reduce overall vulnerability when coverage is high. With rates falling among children and the season lasting longer, officials are urging attention to vaccination while examining changing transmission patterns.