INTRODUCTION

Pertussis is a highly contagious acute respiratory disease; Every 3 to 5 years, there are outbreaks of this disease¹. In the United States, 15,609 new cases were reported in 2018². Tetanus, a disease caused by the Clostridium tetani, is highly fatal; In 2016, it presented an incidence rate of 0.01 per 100,000 inhabitants in the United States^3,4. Likewise, diphtheria is an acute transmissible infectious disease caused by toxigenic strains of Corynebacterium diphtheriae. Although the incidence of diphtheria cases/ has been decreasing year after year^4,5, in October 2020, new cases of this disease were reported in Peru after almost twenty years of absence⁶. This regrowth also occurred in Paraguay, Venezuela, the Dominican Republic, and Haiti⁷. Currently, the prevention of these three pathologies occurs with global and national vaccination schemes⁸, contemplating three doses of the DPT vaccine at two, four, and six months of age in children under one year of age⁹. .

One of the pillars for the eradication and control of diseases is to ensure adequate vaccine coverage; Compliance with the DPT vaccination schedule must be guaranteed at no less than 85%^10,11. Unfortunately, this compliance is hampered by different sociodemographic, economic, and environmental factors.

Increasingly non-compliance with vaccination schedules that include more than one dose is observed in countries such as the United States, Canada, the Netherlands, and Mexico^12-14where it is described that the number of children who comply with the first dose is between 80 to 89%^12-15, while for the following doses compliance tends to decrease between 10 to 15%^12,13, in additional factors such as children born in rural areas, parents with a lower educational level or type of economic condition¹³that would make this goal of complying with the vaccination schedule difficult year after year.

One of the pillars for eradicating and controlling diseases is to ensure adequate vaccine coverage, where compliance with the DPT vaccination schedule must be guaranteed at no less than 85%^10,11. Unfortunately, compliance with the vaccination schedule is hampered by sociodemographic, economic, and environmental factors.

In Peru, according to data from the Ministry of Health (MINSA), through a teleconference held on January 11, 2019, it was found that national coverage of DPT was 78.5% in 2014; in 2015, 87.6%; in 2016, 88.6%; in 2017, 82.3% and for the year 2018 this was reduced to 81.2%¹⁶, with an expected coverage goal of 85.5%⁸; while in samples carried out in micro-networks of Lima, as is the case of the district of San Martin de Porres, it is observed that the coverage was 58.6%¹⁷.

The factors that are associated with non-compliance with vaccination have been described in international studies, but very few have focused on determining whether the economic status and the implications of this at the social level are determining factors in complying with an adequate vaccination schedule. Therefore, it is necessary to carry out studies that allow knowing in greater detail the situation of compliance with the DPT vaccination scheme and the factors that are associated with it, as it is an immunization strategy that avoids the complications of three such relevant and deadly diseases^1,3,5.

Socially, compliance with this health strategy impacts children since they will have better development and growth. However, the most important impact is observed in reducing the infant mortality rate, one of the priorities established by the United Nations (UN) for 2030¹⁰.

above, the objective of this research was to determine the factors associated with non-compliance with the DPT vaccination schedule in Peru in 2019.

METHODS

RESULTS

The population was 7187 mothers with children older than six months of age. Each mother of these children provided relevant sociodemographic information and reported the children's vaccination status.Table 1shows the general characteristics of the study population. It can be seen that, of a total of 7,187 women surveyed, 83.9% (6,029) were between 20 and 39 years old. In relation to their education, women "without education" or with "only primary" were 19.7% (1416). 73.7% (5,299) lived in an urban area and 26.3% (1,888) in a rural area. In addition, 49.7% (3,571) belonged to the poor and poorer economy range. The majority of women had health insurance, represented by a percentage of 76.2% (5477). However, 23.8% (1710) did not have insurance. 29.9% (2,150) had only one child, while 71.1% (5,037) had two or more children.

Regarding the DPT vaccination status of the children of the women surveyed, there were 21% (1508) of children whose vaccination record was incomplete. InFigure 1, it can be seen that departments such as Puno, Loreto, Madre de Dios, Amazonas, and Lambayeque have the highest incomplete DPT vaccination schedule.

Figure 1: Map of Peru and incomplete DPT vaccination, with respect to each department 

Table 2shows the vaccination status for each dose of the applied vaccine in greater detail; it was found that 94.1% (6 760) of the mothers had their children vaccinated with the first dose, as confirmed in the vaccination record, while the "unvaccinated" is 5.9% (427). Regarding the second dose of DPT, the percentage of mothers with vaccinated children is 88.2% (6 340), the "unvaccinated" for this dose is 11.8% (847). Finally, the third dose of the DPT vaccine has a percentage of vaccinated 79% (5 679), and those "unvaccinated" in 21% (1 508).

The unvaried analysis is shown inTable 3, in relation to an incomplete DPT vaccination of the children and the variable "number of children" reported by the mother (1 507), it was observed that 5.6% (405) had a single child and 15.3% (1 102) had two or more children, resulting significant with a PR=1.16, p=0.04. The analysis of the variable "type of residence" analysis found that those who reside in a rural area and have incomplete vaccination are 5.8% (419). In contrast, mothers living in urban areas cover 15 1% (1 088); in this analysis, the PR= 1.10 was insignificant, with p=0.12. The analysis with "type of education" and incomplete vaccination shows us that 4.7% (337) have no education or only attended primary school, the group that had secondary education or higher, is 16.3% (1171), with a PR= 1.22 and p=0.04. When analyzing with the variable of "having health insurance" and incomplete vaccination, it was found that 15% (1081) have insurance, while 5.9% (426) do not have insurance; this relationship had a PR= 1.35 with a p<0.01. Regarding the variable "wealth index" and the incomplete vaccination status, the results obtained show that a PR was found: 1.27, 95% CI: 1.14-1.43, p < 0.01 with respect to families “very poor” and “poor.” Age was significant with a PR: 1.72, 95% CI: 1.50-2.00, p<0.001.

The results of the multivariate analysis, intable 4, show that after controlling the other predictor variables, the incomplete DPT vaccination schedule was associated with the index of poor wealth (RPa:1.21; CI95%:1.05-1.39, p<0.01), not having insurance (RPa:1.41; CI95%:1.23-1.60, p<0.01), without education or only primary school (RPa:1.19; CI95% : 1.02-1.40; p=0.01), age under 20 years (PRa:2.63; 95% CI:2.06-3.35, p<0.01) and having two or more children (RPa: 1.36; 95% CI: 1.19-1.57, p<0.01).

DISCUSSION

This study found that the factors significantly associated with non-compliance with DPT vaccination in Peru in 2019 were: level of education, age, wealth index, not having health insurance, and having two or more children, for bivariate analysis; and the factors, poor or very poor wealth index, not having insurance, no or only primary education, age under 20, and having two or more children by multivariate analysis.

The creation of the WHO/PAHO Immunization Program has been one of the most valued public health strategies and one that contributes to equity. One of the pillars of the success of the programs is to achieve high vaccination coverage. The main indirect indicator of program development is the third dose of DPT vaccine¹⁸.

In this study, it was found that the first dose of the DPT vaccine schedule reached 94.1%. In comparison, the percentage of mothers whose infants did not receive this dose was 5.9%, an appropriate figure according to the UN^14,15, since the organization qualifies values above 85% as an expected percentage of vaccination. In the following doses, the proportion of mothers who had their children without vaccination increased, with 11.8% and 21.0%, for the second and third doses, respectively. It is alarming to see that, when analyzing in a general way, the percentage of complete DPT vaccination in infants is only 79%, a figure below the parameters suggested by the relevant health entities. Gilbert et al.¹³and Scheepers et al.¹⁹carried out similar studies in which the complete coverage of this type of vaccine reaches values between 84.5% and 98%, which is higher than that found in this study. Similarly, in the study by Hadjipanayis et al.⁽²⁰carried out in Cyprus in 2018, it is highlighted that the population of infants not vaccinated against pneumococcus is only 2%; this gives us to understand that there are circumstances such as the wealth index, the type of place where they live, having health insurance or the type of education of the people²¹whose consequence is that vaccination coverage continues to be low and this represents a major problem with respect to community health.

Regarding the age of the mothers, it was found that being under 20 years old (n=123) was significantly associated with incomplete vaccination of the children (OR: 1.72; 95% CI: 1.50-2.0; p< 0.01), which differs from that reported by Kagone et al.²², who in a study carried out on 4086 children, found no association with respect to the age of the mother and compliance with the DPT vaccination schedule²²in the same way there was no association of the age variable with respect to vaccination in the studies by Kusuma et al.²³and Francis et al.²⁴

The level of education of the mother is a primary factor for compliance and understanding of the importance of a vaccination scheme such as DPT; in this study, the number of mothers “without education or only primary education” represents 19.7%, a similar figure is seen in the study by Kurosky et al.²⁵, where they describe women with a "basic, but not higher" education, at 18.7%. In the bivariate analysis, our study found an association between women with no education or who only had primary education and incomplete DPT vaccination (PR=1.22; 95% CI: 1.06-1.40; p=0.04). . Gilbert et al.¹³also analyzes in their study the level of education of parents in relation to non-vaccination in infants, obtaining an OR=1.99, CI95%: 1.02-3.91, p=0.000, in countries such as Ethiopia where Yismaw et al.²⁶with a population of 301 people surveyed found that parents who "do not know how to read or write" their children had an incomplete vaccination schedule in 45% (OR=7.4, p=0.01) suggests that poor educational level is a factor for "non-vaccination".

Within the sociodemographic characteristics of the mother, the place of rural residence and incomplete DPT vaccination was 5.8% (419), the analysis for this association was not significant (PR= 1.1; 95% CI: 0 .97-1.25, p >0.05). In his study, Scheepers et al.¹⁹, in his study, showed association results since he determined that in places with a low and very low urbanization rate to the vaccination status, he obtained an RR=1.02; CI95%: 1.01-1.32; p<0.05. Furthermore, the study by Gilbert et al.¹³, carried out in Canada, showed that in the regions called "Prairies" that constitute the rural and wild area of this country, "non-vaccination" was related to this type of places with an OR= 4.92, p< 0.01. The studies analyzed show us that if there is a relationship with respect to the mother’s place to comply with the vaccination schedule, our results did not find this association.

By dichotomizing the wealth index variable. The percentage of mothers with a “poor and very poor” wealth index and the relationship with incomplete DPT vaccination was 11.5%, this relationship obtained a PR: 1.27, CI95%: 1.14-1.43, p<0.01; in other investigations such as Scheepers et al.¹⁹and Gilbert et al.⁽¹¹⁾found an association with respect to the family wealth index and non-compliance with the vaccination schedule with OR=2.14, 95% CI: 1.10-4.14, p<0.05, but the description of the “low income” per family differs a lot from the Peruvian reality, since they highlight that these incomes are less than 5,000 dollars per month, while the definition of poverty in Peru shows a monthly income of approximately 500 soles, which is equivalent to 135 US dollars; In studies in our country, the author Chuquin²⁷analyzed the association between the wealth index and vaccination in children under five years of age, finding a significant association (p<(0.01) between these variables, while Vásquez et al.²⁸did substantialsignificant results regarding this association (RPa:0.9, CI95%: 0.64-1.25, p=0.21); Faced with these results, we can see that in similar realities the association is presented in certain studies, and it is also suggested that in countries with greater economic scope this association is visualized in greater detail.

Added to the wealth index, the fact of having or not having health insurance must be analyzed, so when analyzing our data we obtained that the number of mothers without health insurance and who do not have a complete DPT vaccination schedule is 5 .9% (476), in the bivariate analysis, a PR= 1.35, p <0.001, was found. The antecedents support this value since in the investigations of Khan et al.²⁹found a significant association (p=0.03) in the relation between not having health insurance and incomplete vaccination status of the infant similarly at the South American level, it was found in the results of the study by Hoz et al.³⁰, also a significant association (OR: 1.8; 95% CI: 1.2-2.4; p<0.001) with respect to the previously described problem³⁰. This shows that having health insurance allows women and families to overcome the financial burden to take advantage of necessary health care facilities.

Within the variables, the number of children was analyzed with respect to the vaccination status, in this case it was found that mothers who have two or more children and the incomplete vaccination schedule cover 15.3% (1102) with a PR= 1.16, 95% CI: 1.05-1.28, p=0.04, considering this characteristic as a prevalence factor. A. Hadjipanayis et al.²⁰, in their investigation, found that the rates of non-compliance with the DTP scheme were statistically significant in the second or third child (p <0.05), a similar case manifested by Lernout et al.¹⁴obtaining HR=1.47, CI95%:1.12-1.8, p<0.05 for the third or fourth child born in relation to the incomplete DPT vaccination schedule¹². This suggests that children older than six months of age, from families with two or more children, are likely to be noncompliant with the DPT vaccination schedule.

When adjusting the variables related to the incomplete vaccination of the children of the mothers surveyed, in the multivariate analysis, it was obtained that the index of poor wealth (RPa:1.21; CI95%:1.05-1.39, p< 0.01), not having insurance (RPa:1.41; 95% CI:1.23-1.60, p<0, 01), without education or only primary education (RPa: 1.19; 95% CI: 1.02-1.40; p=0, 01), age younger than 20 years (RPa: 2.63; 95% CI: 2.06-3.35, p< 0.01) and having two or more children (RPa: 1.36; 95% CI: 1 .19-1.57, p<0.01), were statistically significant and resembled the results obtained from the research cited for this article^{11,19,20,22-29}.

This research presents the limitations of a retrospective, observational study with secondary bases. However, it is robust because it uses representative data, with probabilistic and stratified sampling, on a national basis. Additionally, the proper use of databases with weighting factors and sufficient statistical power for bivariate and multivariate analysis was applied.

CONCLUSIONS

It is concluded that sociodemographic factors related to the mother, such as having two or more children, poor wealth index, not having health insurance, being under 20 years of age and not having an education or only having completed primary school are associated with their children have a noncompliance in the DPT vaccination schedule.

RECOMMENDATIONS

The development and complexity of immunization programs require strategies and not only that vaccination coverage be high to maintain the protection threshold, but also modernize and be inclusive, emphasizing rural populations, with less education, poor access to health systems and poor economic conditions; since this vaccine helps in cognitive development and educational achievement in children.