On-time vaccination coverage in premature infants in Ontario, 2002-2009

Objective — Premature children are at increased risk of complications from vaccine-preventable diseases and should be vaccinated with the routinely recommended childhood vaccines at the same chronological age as full-term infants with the exception of the hepatitis B vaccine for infants of HBsAg-positive mothers. We sought to compare on-time vaccination levels in premature children for recommended vaccinations to levels in children born at term.

Methods — Using linked health administrative databases, we compared the proportion of term (37+ wks), near term (33-36 wks), very premature (28-32 wks) and extremely premature (≤27 wks) children who received at least one vaccination during the 2-, 4- and 6-month vaccination visits within the recommended time period in the province of Ontario.

Results — When we excluded children who were hospitalized at any time during the vaccination window, we identified that vaccination rates were within 3% of each other in the 4 categories examined. However, when we included infants who may have been hospitalized at any point during the on-time window, we observed substantially lower rates in the extremely premature children at 2 and 4 months and in the very premature children at 2 months.

Conclusion — Our study identifies the need to confirm whether vaccinations are given while premature children are in hospital during the time of their scheduled vaccinations.