What timing of vaccination is potentially dangerous for children younger than 2 years?

Abstract

Vaccine-preventable diseases still occur although measured coverage rates at 2 y of age are high. The occurrence of these diseases may be explained in part by untimely, that is, late vaccination. Our objective was to identify potentially dangerous vaccination delays for each dose of each vaccine in children younger than 2 y. A 3-round Delphi process was conducted by e-mail. We recruited 37 French experts in vaccines for children: 16 from the Infovac-France group and 21 from the French study group for pediatric infectious diseases. Items were generated by a literature review for the 10 vaccine doses recommended before 2 y of age. Item reduction in round 1 and 2 and any consensus in round 3 used a 70% consensus cutoff. The mean participation rate was 79%. Delays that should not be exceeded were identified for all vaccine doses. The 70% consensus was reached for 6 of the 10 vaccine doses: 15 d after the recommended date for the first 2 doses of the diphtheria-tetanus-acellular pertussis-inactivated polio vaccine/Haemophilus influenzae b vaccine and for the second dose of the pneumococcal conjugate vaccine, 1 month for the meningococcal C vaccine and for the first dose of the measles-mumps-rubella vaccine, and 11 y of age for completion of the hepatitis B vaccination. This Delphi process identified potentially dangerous vaccination delays for children to the age of 2 y. These can be used as new indicators in further studies of vaccine effectiveness and can help to improve the quality of vaccine protection in children.

Reply to Editorial on “What is a potentially damaging vaccination delay in 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.…”

Timeliness of vaccination in infants followed by primary-care pediatricians in France

“…In our study, immunization delays were based on the definition of a potentially dangerous immunization delay obtained by a Delphi method taking into account epidemiologic data for each disease and age for each injection. 9 Therefore, our study provides more precise data compared to previous studies. At 2 and 4 months of age, the mean period of delay was 30 to 44 days after the defined deadline.…”

“…A potentially dangerous immunization delay was defined by a real age of vaccination over the age at risk as identified in a previous Delphi study (Table 1). 9 Vaccination delays, presented Table 2, were calculated in days between the age at risk 9 and the real age of vaccination.…”

“…8 The results of a Delphi study which defined what a potentially dangerous vaccination delay is, were recently published. 9 This process included French experts in vaccination and pediatric infectious diseases specialists. They determined limits of the potentially dangerous vaccination delay of the 10 vaccinedoses recommended for French children aged less than 2 years.…”

Vaccine-Preventable Diseases Requiring Hospitalization

“…30 Expert consensus suggests that a delay of 15 days to 1 month for the first dose of most vaccinations represents a "potentially dangerous delay." 31 We found that Amish children had an increased risk of VPD requiring hospitalization compared with non-Plain children. Most, but not all, of this increased risk was driven by differences in vaccination coverage (r = −0.65).…”