Reply to Editorial on “What is a potentially damaging vaccination delay in children younger than 2 years?”

ABSTRACT

Vaccine guidelines should be followed at the best to avoid vaccine preventable diseases in children and particularly in at-risk children. The authors of the editorial rightly emphasize the risk of hepatitis B in unimmunized children. Vaccine delays are frequent and indicators of vaccine delays are needed. Thresholds that identify an important increase in relative risks are the most relevant, for hepatitis B as well.

KEYWORDS:

• children
• dangerous delays
• hepatitis B
• timeliness
• vaccines

Dear Editor,

We read with interest the Editorial by Kane MA et al.,¹ about our article entitled “What timing of vaccination is potentially dangerous for children younger than 2 years?.”²

We fully agree with the arguments extensively and well reminded by these authors about the importance and the burden of the hepatitis B infection in general and in France in particular. We share their preoccupation not to delay the hepatitis B vaccination in the general population of infants and particularly in at-risk newborns or children. A strong attention has been paid to this point in the discussion of our article. It is the reason why we have mentioned in our study that right ages of vaccination are those presented in the official guidelines (i.e., early in infancy). We did not wish to substitute the official thresholds to others. Any delay can be detrimental for any vaccine dose, including hepatitis B vaccine doses.

Although there is a risk of hepatitis B during infancy and childhood, this risk strongly increases in adolescents and young adults. This is probably the main reason for the choice of this 11-years threshold by the experts. The experts did not ignore the risk of hepatitis B transmission among children in France with a higher risk of chronic disease. The degree of increased risk may have been appreciated differently, as it was appearing in the first round of the Delphi: 41% of the experts had chosen 16 months of age as a limit to complete the full hepatitis B vaccination when 31% had chosen 11 y. To determine the hepatitis B vaccine delay, the experts have probably considered the following issues: (1) hepatitis B prevalence in France is low (less than 1–2%), as mentioned in this editorial. (2) Although chronic hepatitis B was mainly the result of mother to child or child to child transmission in endemic countries, it is unclear in France: the proportion of chronic hepatitis B is low (5%) when acquired in adulthood and high when acquired in neonatal period (90%). But the number of infected adults is high (mainly sexual transmission or drug users) and the number of infected neonates is small, which results in a higher number of chronic cases when hepatitis B is acquired after adolescence. (3) Indeed, the hepatitis B prevalence in pregnant women in France is also low (0.72%).³ Even if the risk of mother-to-child transmission persists, it has been dramatically reduced worldwide by a systematic hepatitis B screening during pregnancy and the administration of immunoglobulin and hepatitis B vaccine in susceptible neonates.⁴ In France, even in an at-risk cohort of HIV and hepatitis B positive pregnant women, and based on this strategy, none of the children have been infected.⁵

Indicators are needed to measure the evolution of vaccination timeliness and the importance and frequency of vaccine delays. Vaccination delays are frequent in clinical practice,^6,7 and may have important consequences that can be assessed by pediatricians working in intensive care units. Our Delphi study sought to determine thresholds that corresponded, for the experts, to a strong increase of risk of the vaccine preventable disease, considering the age-related prevalence, the epidemiology and the severity of the vaccine preventable-diseases in children.

In conclusion, vaccine guidelines should be followed at the best to avoid vaccine preventable diseases in children and particularly in at-risk children. The authors of the editorial rightly emphasize the risk of hepatitis B in unimmunized children. Indicators of vaccine delays are needed. Thresholds that identify an important increase in relative risks are the most relevant. This is the case in adolescence for hepatitis B.

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed.