Abstract
Delay in vaccination from schedule has been frequently documented and varies by vaccine, dose, and setting. Vaccination delay may result in the failure to prevent deaths that would have been averted by on-schedule vaccination.We constructed a model to assess the impact of delay in vaccination with pneumococcal conjugate vaccine (PCV) on under-five mortality. The model accounted for the week of age-specific risk of pneumococcal mortality, direct effect of vaccination, and herd protection. For each model run, a cohort of children were exposed to the risk of mortality and protective effect of PCV for each week of age from birth to age five. The model was run with and without vaccination delay and difference in number of deaths averted was calculated. We applied the model to eight country-specific vaccination scenarios, reflecting variations in observed vaccination delay, PCV coverage, herd effect, mortality risk, and vaccination schedule. As PCV is currently being scaled up in India, we additionally evaluated the impact of vaccination delay in India under various delay scenarios and coverage levels.We found deaths averted by PCV with and without delay to be comparable in all of the country scenarios when accounting for herd protection. In India, the greatest relative difference in deaths averted was observed at low coverage levels and greatest absolute difference was observed around 60% vaccination coverage. Under moderate delay scenarios, vaccination delay had modest impact on deaths averted by PCV in India across levels of coverage or vaccination schedule. Without accounting for herd protection, vaccination delay resulted in much greater failure to avert deaths.Our model suggests that realistic vaccination delay has a minimal impact on the number of deaths averted by PCV when accounting for herd effect. High population coverage can largely over-ride the deleterious effect of vaccination delay through herd protection.
Highlights
Vaccines prevent 2–3 million deaths each year [1]
We explored the effect of pneumococcal conjugate vaccine (PCV) vaccination delay on S. pneumoniae mortality in children under five in various country-specific scenarios using a model for estimating the impact of vaccination on child mortality by fine age intervals
The greatest absolute difference in number of deaths averted was observed for Nigeria, where a moderate vaccination delay and low three-dose coverage resulted in 600 additional deaths equating to 3% of the total deaths averted by PCV
Summary
Vaccines prevent 2–3 million deaths each year [1]. A high proportion of vaccine-preventable deaths occur in early infancy. While some deaths cannot be directly prevented because of the minimum age of vaccination, delay in vaccination from schedule can result in preventable deaths. Numerous studies have documented delays in vaccination in multiple settings [2,3,4,5,6,7,8]. Evidence from Sanderson and colleagues suggest delay in vaccination is common, the degree and frequency of delay varies greatly by vaccine, dose, and country. Median vaccination delay across low- and middleincome countries (LMICs) in 50% coverage ranged from two weeks for bacille Calmette-Guerin (BCG) to six weeks for the third dose of diphtheria-tetanus-pertussis (DTP), with a handful of countries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
