Although
injections administered during the incubation period of wild poliovirus
infection have been associated with an increased risk of paralytic
poliomyelitis, quantitative estimates of the risk have not been established. During a
poliomyelitis outbreak investigation in Oman, vaccination records were reviewed for 70 children aged 5-24 months with
poliomyelitis and from 692 matched control children. A significantly higher proportion of cases received a DTP (
diphtheria and
tetanus toxoids and
pertussis vaccine) injection within 30 days before
paralysis onset than did controls (42.9% vs. 28.3%; odds ratio, 2.4; 95% confidence interval, 1.3-4.2). The proportion of
poliomyelitis cases that may have been provoked by DTP
injections was 35% for children 5-11 months old. This study confirms that
injections are an important cause of provocative
poliomyelitis. Although the benefits of DTP vaccination should outweigh the risk of subsequent
paralysis, these data stress the importance of avoiding unnecessary
injections during outbreaks of wild poliovirus
infection.