The effect of low birth weight on timing to BCG vaccination in a rural district of Northern Ghana

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Introduction: Early Bacille Calmette-Guérin (BCG) vaccination of low birthweight (LBW) infants has been shown to have heterologous immunological effects by increasing the in vitro cytokine responses which contribute to the maturation of the infant immune system and thereby protecting against fatal infections in the neonatal period. It has been noted to also reduce neonatal mortality in these LBW infants. In some low-income countries, BCG vaccination is usually postponed for children born with a low birthweight (LBW). This has resulted in delayed timing to BCG vaccination. Ghana, however, does not have any restrictions on receiving BCG vaccination for LBW infants. This study therefore assessed the effects of low birthweight on timing to BCG vaccination in a context where there are no restrictions on vaccinations. Methods: The study used maternal and child health data collected from the Navrongo Health and Demographic Surveillance System (NHDSS). Age at BCG vaccination was the main outcome variable of interest whilst the weight at birth of the child was the main primary exposure variable. Frequencies, proportions, median and inter-quartile ranges (IQR) were used to describe the participants. Lognormal accelerated failure time (AFT) models were conducted, and time ratios obtained to assess the effect of birthweight on timing to BCG vaccination. Logistic regression models were also used to assess the factors associated with delays to BCG vaccination. Results: About 12% of the infants were low birthweights (less than 2500 grams) with 17% weighing less than 2000 grams and 83% weighing between 2000 and 2490 grams. The results showed than low birth weight infants had a median vaccination age of 2 days compared with normal birth weight (≥2500 grams) infants who had a median of 3 days. No statistically significant difference in time to BCG vaccination by birthweight status was observed. However, other characteristics which were statistically significantly associated with time to BCG included level of education of mother, place of delivery, socio-economic status of family and the age of mother. Conclusions: The study shows that low birthweight infants in the study area receive BCG vaccination as timely as normal birthweight infants with several maternal and infant characteristics as well as socio-demographic and health system factors been associated with the timing. It demonstrates that low birthweight infants can receive BCG vaccination on time if there are no restrictions regarding vaccination schedules.