Vaccines are among the safest medicines to use, and these are considered a very effective tool for preventing infectious diseases. Like any other drug, no vaccine is 100% effective or 100% safe at 100%of times [1]. Serious adverse effects have been reported with the DTwP vaccine but are rare. The frequency of these side effects/1000 doses is 0.2-4.4 for fever more than 40.5 C, 4-8.8 for persistent crying, 0.06-0.8 for hypotonic hyporesponsive episodes, 0.16-0.39 for seizures, 0.007 for encephalopathy [2].

Despite these methodologic difficulties, the National Childhood Encephalopathy Study (NCES) and other controlled epidemiologic studies have proved that DTP can cause acute encephalopathy [3-7]. This adverse event rarely occurs, with an estimated risk of zero to 10.5 episodes per million DTP vaccinations [7]. A detailed follow-up of the NCES indicated that children who had had a severe acute neurologic illness after DTP administration were significantly more likely than children in the control group to have chronic nervous system dysfunction ten years later. These children with chronic nervous system dysfunction were more likely than children in the control group to have received DTP within seven days of onset of the original acute severe neurologic illness (i.e., 12 {3.3%} of 367 children vs six {0.8%} of 723 children) [8]. Our purpose is to understand the severe DTP vaccine-associated reactions further.

A 2-month-old male infant presented to the emergency pediatrics outpatient of our hospital with complaints of fever and abnormal body movements (multiple episodes). His medical history revealed that the patient was well 02 days back; when he started complaining of fever which was not documented, the patient was warm to touch to mother; for the same illness, the patient was given paracetamol.

Fever subsided after taking paracetamol. Then after 5 hours of the onset of fever patient had episodes of abnormal body movements in the form of jerky movements of bilateral upper and lower limbs. His antenatal history and perinatal history was uneventful. No record of epilepsy in the family. It was elicited from the history that the patient had pentavalent immunization in the morning.

The most severe reaction in pertussis vaccination was the neurologic side effects such as seizures and encephalopathy, which are related to the whole-cell pertussis vaccine. With the introduction of the acellular vaccine, these adverse effects have been reduced significantly [9,10]. Side effects of whole-cell pertussis vaccine are significantly higher than those of acellular vaccine because acellular pertussis vaccine contains 2–5 proteins. In comparison, the whole-cell vaccine contains approximately 3000 proteins, and again the whole-cell vaccine contains endotoxin, known as a neurotoxin, pertussis toxin, and adenylate cyclase [10]. In a recent retrospective study in the US following a huge outbreak of pertussis in California, the researchers found that the 5-component aP vaccine had an estimated efficacy of 88.7% [95% confidence interval (CI), 79.4–93.8%] [11]. A Cochrane review by Zhang et al. after studying six aP vaccine efficacy trials and 52 safety trials concluded that the efficacy of multicomponent (≥3) aP vaccines varied from 84% to 85% in preventing “typical whooping cough” and from 71% to 78% in preventing mild disease. In contrast, the efficacy of one- and two-component vaccines varied from 59% to 75% against typical whooping cough and from 13% to 54% against mild disease [12]. However, a few countries have demonstrated high levels of effectiveness of mono- and bicomponent aP products in preventing pertussis by employing them in their immunization programs [13]. The available evidence is not sufficient to establish any significant difference in vaccine effectiveness of aP vaccines with differing numbers of components [14]. The “murine intracerebral challenge test” has been considered as a “gold standard” for wP vaccines and has been used to standardize and assess the potency of wP vaccines [15]. In a comprehensive study, Huang WT et al. [16]. Retrospectively evaluated 433.654 infants aged between six weeks and 23 months and found no statistically significant increase in the risk for suffering convulsions within the first three days after DaBT-IPA-Hib vaccination. Berkovic et al. [17]. Studied 14 patients who had their first seizure within the first 72 hours after vaccination and who were then followed up with the diagnosis of resistance epilepsy, and they found a mutation in SCN1A encoding alpha one lower unit of the sodium canal. The authors concluded that encephalopathy-resistant convulsion might be associated with genetic epileptic syndromes.