Our analysis showed large differences between vaccination coverage in each province. In some medical facilities, the vaccination coverage was even more than 100%. This does not mean that some children were vaccinated twice, but more children than before. It was a case in 10 health facilities in 3 provinces. The lowest coverage was in provinces, where at least 60% of the population lives in areas not accessible by road. The access to services can be, in these provinces, the biggest problem in vaccine delivery. The vaccination coverage only in one province (Morobe) was equal to median vaccination coverage in PNG. Moreover, one province (Chibu) within the analyzed period experienced a marked decline in vaccination rates – to rates lower comparing to the country average.
There is often only one static clinic per week at the health center level in PNG, resulting in long waiting times for services. Although vaccinations are free of charge, some health facilities require user fees to run the operational costs. This discourages attendance at clinics unless the child is sick. It is proved by a mean number of outpatient visits per person per year, which in PNG is 1.28 (13). Neonatal mortality and under 5-year mortality are among the highest in this region of the world (57/1000 live births) (1,2,10). Services provided by the healthcare facilities also experience many troubles: lack of vaccinations, 30% of healthcare facilities are experiencing problems with vaccinations supply, or problems with maintaining cold chain (10). The other problem is a suboptimal number of healthcare professionals. According to PNG's official data, there are 32 pediatricians, 0.5 physicians per 10,000 population, and 5.3 nurses per 10,000 population (2).
PNG has a relatively low coverage of essential services (Universal Health Coverage), according to WHO (12). Antenatal care is an indicator of access to and use of health care during pregnancy, and its low use is one of the well-known risk factors for incomplete vaccination. Mean antenatal care use in PNG is estimated at 54% (13). In regions with the lowest use of antenatal care, CHS's vaccination coverage was also low. In a study conducted by Russo in Cameroon, children born at health facilities had a higher immunization coverage rate than those born at home (14). The percentage of supervised deliveries in PNG is estimated at 37% (10).
The other problem is the lack of public understanding of the need for vaccinations (15,16). There are huge difficulties in communication. The adult literacy rate is estimated at 63.4 % (1). So far, no opposing opinions about vaccinations have been noticed in PNG, but the understanding of the idea of vaccinations is poor. For some people, there is no difference between vaccination – prevention and treatment. They view injection as a treatment and think there is no need to give them healthy children. The expected benefit of participation in the survey can be raising awareness of vaccinations and their importance in protection for children and adults.
Natural disasters and military conflicts also cause difficulties in access to health services.
On 26 February 2018, the earthquake took place in four provinces (Hela, Southern Highlands, Western Province, and Enga). 544,000 people were affected (46% children; 17,419 children in age 0-12 months). This natural disaster was then followed by inter-communal fighting in Hela Province.
This also caused considerable problems in vaccination. Out of 86 health facilities,18 were severely damaged. UNICEF estimated that only 10% of the target population (children younger than five years) received pentavalent and MR vaccination in this province (17).
According to the National Health Information System, the measles vaccine coverage in 2016 was 51% (10). None of the provinces reported over the target 80%. The proportion of districts reporting less than 50% DTP3 (all three doses of vaccine) coverage was as high as 60%. Only 8% of provinces reported vaccination coverage greater or equal to 90%.
Data concerning the vaccine coverage obtained from CHS are much lower than the official ones. Data recording and reporting in health facilities was a shortcoming, identified earlier by researchers performing studies in PNG (18,19,20). Wiesen, in 2014 in a study on assessing the hepatitis B birth dose vaccination program in PNG, found out that only 17% of the health facilities were able to provide a vaccination coverage figure.
A lack of reliable demographic data also causes the problem with the estimation of vaccination coverage. In PNG, birth and death registration systems are not yet sufficiently developed to estimate a birth cohort accurately. The population is growing very fast; hence, an entire birth cohort seems to be more significant. The latest polio epidemic showed that the pediatric population might be bigger than assumed. In the first round of catch-up vaccination action covering the three high-risk provinces, the estimated number of children was 289,582, but 303,907 (105%) children under five years old were vaccinated (4). As a result of the recent polio campaign, 15/56 patients had proof of at least one dose of OPV.
A field survey is another way to obtain the vaccination coverage. It can be done by checking patients' vaccination records. However, in PNG, the so-called baby book is missed very often. In a survey conducted by Samiak, according to medical records of 70 patients and based on the interview with parents, only 15% of children had complete vaccination status (16). In our analysis, 68 % had no vaccination records. Based on vaccination records, half of the patients had only one vaccination visit.
The main limitation of the study is a small sample of questioned parents. Taking into consideration local customs, it is challenging to schedule extensive studies in PNG. Indigenous people are very wary of contact with strangers. There is a shortage of healthcare professionals in PNG, and because of their workload, they are not very eager to be involved with surveys. So this is why we should have accepted this small study as the only possible way of gaining insight into PNG vaccination practices.
Improving vaccination coverage in PNG is essential for outbreak control. It is necessary to improve the quality of services delivered by healthcare facilities and increasing community awareness of the role of vaccinations. Declining coverage rates observed in our analysis are in accordance with data provided by GAVI, WHO, and Country Official estimates. This is a very worrisome trend.