Although vaccines used in the country immunization program are safe and very effective, no vaccine is completely safe and there might be some adverse events following immunization using any of them(12) . On the whole, the amount of adverse events following immunization are low in Iran and most of which are reported to be mild and temporary and are mostly removed without any medical treatment(13) .The results showed that the general incidence of adverse events in DPT and Pentavalent were0.2% and 0.3%, respectively. The high fever and mild localized complication were reported to have the highest incidence in DPT (47.7%) and Pentavalent (31.68%) among other adverse events.
Firstly, it seemed that Pentavalent adverse events number was more than the DPT ones (0.3% vs. 0.2%), but a closer look at the results revealed that most of the Pentavalent reported adverse events were localized and mild, whereas those related to DPT were mostly associated to high and severe fever. On the other hand, the increase in the Pentavalent adverse events reported in 2015compared to DPT ones reported in 2013could be justified through the general increase in the number of adverse events reported throughout the country and increasing the ability of the care and health system in identifying and recording more vaccine adverse events in 2015 compared to2013. Moreover, the results showed that the most frequent adverse events reported were high fever(47.4%)and localized mild events (31.68%)for DPT and Pentavalent and the highest number of adverse events (about95%) was associated to reactions to the vaccines in general. The study also showed that there was a significant relationship between the kind of vaccine with the type of reaction, adverse events categorization, the infants’ gender and place of residence (p<0.05).
In fact, at least one out of four infants having received the vaccines showed some kinds of adverse events which were mostly associated to fever(14). Fever could generally be produced after receiving all kinds of vaccines. This study showed that high fever was the most common adverse event of DPT (%47.4) whereas it was28.15%for Pentavalent. Severe localized events were reported to be 13.16%in DPT whereas this was half for Pentavalent (about 7.83%). The convulsion cases due to high fever reported to be similar in both vaccines; but vomiting and diarrhea were reported to be much more in DPT compared to Pentavalent. (8.2% vs. 1.58%). Moreover, injection site abscess was reported to be more in Pentavalent than DPT (3.28% vs. 1.58%).
Similarly, in studies by Sharifi et al.(9) and Ayatollahi et al.(15) High fever was reported to be the most frequent adverse event of DPT vaccine. Mansour et al. in Newzeland reported longtime crying among infants who had received DPT(16). Al-Jadiryinin Iraq reported pain and inflammation as the most common events of DPT(17). Barkin et al. reported that 54% of the infants received the vaccine showed fever as the most common event(18). In a study by Suser et al, localized pain, redness, fever and edema were reported to be the most common adverse events of DPT(19). The benefits of childhood vaccines far outweigh any potential risks. Significant global data on vaccination showed that lack of Hib vaccination caused a significant amount of disease and mortality among infants. Therefore, WHO strongly recommends global Hib Vaccination(20). Pentavalent vaccination automatically increased the coverage of Hepatitis B and Hib immunization(11).
In addition, the results of different studies show that pentavalent vaccine was safe and tolerable and possessed a high level of immunizing for all molecular antigens and some biological reactions(21-24). This vaccine was tested for10 years from 2002(when its use started in Ghana) to2012 (when its use started in India) in some Asian countries(24). The results of these studies showed that the most common reported adverse event of Pentavalent was localized mild events. A study by Indian Institute of Serology showed that local reactions to Pentavalent vaccine included pain, redness and edema in the injection site and its general systematic reactions reported to be fever, unusual crying and irritability(25) . Hatami et al. in Tehran, reported fever as the most common adverse event of Pentavalent (71.2%)(13). In a study in the United States of America, high fever was reported to be the most common adverse event of Pentavalent(26) whereas Cunha et al reported hypo-tony as the most common adverse event for DPT and Pentavalent vaccines(27).
Finally, it should be noted that most parents were aware of the fever following vaccination and they preventively gave Acetaminophen to their infants which could decrease their fever and prevent high fever among them; therefore, the incidence rate of this event might be changed due to the parents' interventions(14) . Categorizing the vaccine adverse events showed that most of the reported events were associated to the reaction to the vaccine which was in line with Raisi et al. in Shahre Kurd(28) and Parisay et al. findings in Kohkiloye va Boir Ahmad(29). In addition, the findings of the study showed that there was not any significant relationship between the infants’ gender with DPT and Pentavalent adverse events. However, the possible complications of the vaccines seemed to be more among males compared to the females. This finding was in line with the findings of Reisi et al. in which there wasn't a significant relationship between the gender of the infants and the vaccines' adverse events(28). Moreover, in studies by Paisay et al.(29) and Ayatollahi et al(30). Although there was not a significant relationship between the infants’ gender and the vaccines' adverse events, the possible adverse events were reported to be more among males compared to the female which was in line to the findings of this study. However, Nabavi et al. reported that the vaccines' adverse events seemed to be more among females than the male which is in contradiction to the findings of this study(31) (32).
However, sever cases associated with the vaccine adverse events lead to hospitalization which included a very small percentage of the vaccinated infants in comparison to the total number of vaccinated ones. The findings of the study show that only 1.5%of all reported complications in vaccinated infants by DPT and Pentavalent led to their hospitalization and the hospitalized cases numbers were almost the same in both vaccines. In fact, many hospitalization cases can be due to other factors contemporarily existing with vaccination procedure.