We want to protect the most vulnerable groups around us.
Two more children died of COVID-19 in Hong Kong.
Whether in war or in the midst of an epidemic, the deaths of children are always the most heart-wrenching thing. Today both are girls, one is 8 years old with thyroid disease and the other is 4 years old with congenital heart disease. Although some of the children who died in hong Kong have underlying diseases, this proportion of deaths is still uncommon in other countries and regions, and for comparison, Singapore currently has many new infections, but so far no children under the age of 12 have died of COVID-12 in Singapore.
Including in 2020, among the earliest more than 40,000 cases in Chinese mainland, there were 416 children under the age of 9, and none of them died.
It is certainly wrong to say that children are not fatal to COVID-19, but compared with middle-aged and elderly people, children with COVID-19 have a much lower proportion of infection, severe illness or mortality.
So what exactly is wrong with Hong Kong?
Image from AP
/ A /
There are currently several explanations for this problem:
Ba.2 variants are more pathogenic in children.
BA.2 is a subspecies of Omicron and is the main variant of the current outbreak in Hong Kong. But I personally do not agree with the statement that BA.2 is the culprit, there is some evidence that BA.2 is more contagious than BA.1, but there is no evidence in humans that BA.2 is more pathogenic, including children. And it's important to note that BA.2 is also a major variant in many countries, such as Singapore, but we didn't find a significant increase in the proportion of severe children or deaths in these countries.
Of course, since the BA.2 pandemic is 6 to 8 weeks later than BA.1, severe illness and death may lag behind, so further follow-up studies are needed.
Childhood vaccination rates in Hong Kong are low.
The vaccination rate of children in Hong Kong is indeed not high, and the vaccination of children aged 5 to 11 years old was not released until January 21 this year, and the vaccination of children in Fubitai was even later than February 16. At present, few children under the age of 11 in Hong Kong have completed two doses of vaccination.
However, the problem of low child vaccination rates is not uncommon, and in many countries and regions, the recommendation of children's COVID-19 vaccination efforts has been met with resistance due to parents' concerns about adverse vaccine reactions, but such a high proportion of child deaths has not been found in other countries and regions. Even as we mentioned above, during the earliest wave of outbreaks in 2020, no children Chinese mainland were vaccinated, but none of them died under the age of 9.
When we want to attribute these problems to sporadic cases, we should first consider all possibilities. In fact, there is speculation in the academic community that, although the evidence is not particularly sufficient at present, it is indeed very worthy of study - the problem of pre-existing immunization decline in Hong Kong children.
/ II /
There are currently 7 types of coronaviruses (HCoV) that can infect humans (Note: The 8th type has been found, but it has not been recognized by the academic community), of which 4 are the symptoms that cause the common cold, and the other 3 are the well-known SARS, MERS and new crown. The common cold is a large class of diseases (hereinafter referred to as colds), and about 25% of all cold cases are pathogens of coronavirus. The presence of cross-reactive antibodies between these seasonal coronaviruses and the new coronavirus, and whether there is cross-protection, has been one of the focuses of research in the past two years. The results of the current study are not the same, and there are some differences. According to a previous study published in Lancet, these seasonal coronaviruses have previous infection-induced antibodies, and the new coronavirus may only cross-react, but there is no effective cross-protection (because the epitope of antigens varies greatly).
However, antibodies are not all immunity, and cellular immunity also plays an important role, and studies have shown that the presence of T cell immunity to seasonal coronaviruses can induce a response to the new coronavirus, including memory B cells and T cells, which are important components of immunity. For example, previous studies have shown that in 20% to 50% of individuals who are not infected with the new crown virus, T cells with cross-reactions to the new crown virus have been found, and there is evidence that these reactions originate from seasonal coronavirus infection, and this phenomenon is more common in children and adolescents.
Therefore, cross-immunity from seasonal coronavirus (as well as other viruses) infection is not long-lasting, but can reduce the severity of the disease.
/ III /
This is a theoretical analysis, and in the real world, we have also observed this phenomenon - it happened in Hong Kong in the autumn of 2020.
According to a previous study published in Emerald Infectious Diseases, in October 2020, when schools in Hong Kong reopened after two long closures (2020.1-2020.5 and 2020.7), despite measures such as mask bans and increased desk spacing, a large number of children in Hong Kong had colds.
The children were not infected with the coronavirus or the flu virus, they were infected with rhinovirus, and in about a month' time, 482 rhinovirus outbreaks were reported in primary and secondary schools, kindergartens and nurseries in Hong Kong. This phenomenon is also happening in other reopened countries and regions, where in September 2020, two weeks after children in the UK returned to school, the rate of rhinovirus infection in the population also rose sharply.
As a result of various public health measures during the COVID-19 pandemic (including mask wearing, distancing and reduced social activities, etc.), the prevalence of a variety of respiratory infectious diseases, including influenza, RSV and multiple rhinoviruses, such as influenza cases in the United States in the winter of 2020 fell by about 100 times.
After reopening, when people's probability of exposure to these pathogens increases, the risk of infection increases significantly due to the decline of existing immunity. Children, in particular, used to maintain a certain level of immunity due to regular exposure to various seasonal coronaviruses, but this immunity gradually subsides in the case of prolonged school closures and lack of social interaction.
As of January this year, primary schools and kindergartens in Hong Kong have been forced to close classes at least four times since the outbreak of the epidemic, and the suspension period has set a record for the longest time in the world. And when children are once again exposed to a real world full of viruses, the problem may arise.
/ IV /
Therefore, some researchers in Hong Kong currently believe that the reason for such a high proportion of child deaths under this wave of the epidemic may be related to the decline in immunity of children in Hong Kong in the past two years.
Of course, to confirm the correlation and causal relationship between the two, more research is needed to confirm it. But the impact of long-term school closures and lack of socialization on children's immunity and mental health should be issues that need our attention, and many of the problems exposed by the epidemic in Hong Kong, including the low vaccination rate of vaccines in the elderly, the record number of deaths per 100,000 people, and the number of child deaths, are very heavy lessons.
Finally, we want to keep exploring viruses, including COVID-19, researching effective vaccines, and improving our public health strategies because we want to protect the most vulnerable groups around us.
Author: Zhuang Shilihe
Editor-in-charge: Zheng Huaju
Proofreader: Zang Hengjia
Plate making: Xue Jiao