It is the winter flu season again in Hong Kong. Since the start of 2018, there were already two young children who died of severe influenza-associated complications. One may wonder, why would this happen every year? And why are young children more susceptible to dying from the flu?

Immune system is not fully developed for young children

The key reason why young children are more susceptible to dying from the flu is because their immune systems are not fully developed. Research points out that during infancy, the young human child is protected against many infectious diseases previously experienced by the mother, since the passive IgG antibody is transferred from the mother transplacentally and in milk. However, once this protection fades away, the newborn becomes more vulnerable to bacterial and viral infections.

According to recommendation from the Centers for Disease Control and Prevention (CDC), everyone 6 months of age and older should get a seasonal flu vaccine. Hence, this implies that for the children younger than 6 months old, it is best to ensure the people taking care of them are vaccinated.

As for children aged 6 months or above, vaccinations remain as the most effective protection, which stimulate protective immune responses in the maturing immune system. In Hong Kong, government officials have repeatedly reminded parents to take their children to get vaccinated against seasonal influenza for better personal protection.

Low uptake for seasonal influenza vaccination is another reason

Low uptake for seasonal influenza vaccination is another major reason causing more young children susceptible to the complications from the flu.

Looking at statistics from the Centre for Health Protection, there are in total 13 paediatric cases of influenza-associated complication/death as of February 7, of which 12 of them did not receive influenza vaccine for the 2017/18 season.

Such phenomenon does not only limit to Hong Kong. A research published in 2017 in the UK has highlighted several factors which hinder many parents from vaccinating their child. One of which is these parents believe that the vaccine is dangerous, and may cause side-effects to their child.

Recently, an audio recording by a Canto-pop stay has gone viral online in Hong Kong. She said in the recording that the seasonal influenza vaccination has “partially” led to the winter flu outbreak. She also accused that the vaccines contain mercuric compound, and that the vaccines were made with chicken eggs without safety checks. She suspected patients began to spread the mutated bacteria after taking the flu shots and being infected.

Following the incident, the Department of Health immediately issued a statement, reiterating that seasonal influenza vaccination is a safe and effective way of preventing influenza and its complications.

Out of 13 paediatric cases of influenza-associated complication/death as of February 7, 12 of them did not receive influenza vaccine for the 2017/18 season.
Out of 13 paediatric cases of influenza-associated complication/death as of February 7, 12 of them did not receive influenza vaccine for the 2017/18 season.

"Influenza vaccine has been in use for 70 years. The vaccine has undergone repeated testing and quality assessment to ensure that it is safe and reliable. In Hong Kong, all currently used influenza vaccines are inactivated vaccines so there is no live virus in the vaccine. People will not be infected with influenza through vaccination and it is also impossible to transmit any mutated virus. Influenza vaccine contains ovalbumin (a chicken protein), but the vaccine manufacturing process involves repeated purification and the ovalbumin content is very little. Even people who are allergic to eggs are generally safe to receive vaccination.

"In addition, the influenza vaccines currently supplied for use in Hong Kong, including the Government Vaccination Programme and in private medical sectors, are all in single dose pre-filled syringes which do not contain a mercuric compound (e.g. thiomersal) as preservative, and there is also no aluminium content," said the spokesman.

More recently, research team from The University of Hong Kong (HKU) published results of a hospital-based study in Hong Kong, which was aimed to estimate influenza VE for the winter of 2017/18. In the analysis, the team included data on 1,078 children who were admitted between 4 December 2017 and 31 January 2018 with febrile acute respiratory illness and who were tested for influenza. There were 339 children with laboratory-confirmed influenza, among which 80% had influenza B. Using the data collected on these children, the team estimated that influenza vaccination effectiveness was 66%. Most vaccinated children had received the quadrivalent vaccine which includes a B/Yamagata strain, rather than the trivalent vaccine that does not include a B/Yamagata strain.

Children may practice poorer personal hygiene than adults

In addition, since the cognitive and functional abilities of young children are still developing, it may be difficult for them to manage and remember a certain amount of health knowledge and practices, even though their parents might have taught them. Hence, they might have worse personal hygiene than adults, thereby exposed to a higher risk for the flu.

Poor personal hygiene can result in increased risk of infection and illnesses.
Poor personal hygiene can result in increased risk of infection and illnesses.

It is also related to the approach of how the parents teach their children, as pointed out by a study published in 2016 in Hong Kong.

The study particularly highlighted that Chinese parents might be more inclined to using controlling and restrictive approaches in teaching their children. However, the effectiveness of such approach is in doubt as frequent use of restrictive or controlling approaches by parents have been associated with children’s behavioural problems such as internet misuse and unhealthy eating.

Instead, the study has suggested a multi-faceted approach involving the health sector, community partners and families in health promotion, as partnerships between community nurses and teachers provide opportunities to strengthen parents’ abilities and knowledge to create healthy households. MIMS

Read more:

Flu vaccines are 66% effective among children with influenza, reports HKU researchers
Have flu vaccine manufacturers been putting their eggs in one basket for too long?
Severe paediatric influenza A infection amid Hong Kong’s summer influenza season