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 that there were more children than before. It was a case in 10 health facilities in 3 provinces, NCD, Enga and Manus. The lowest coverage was in Gulf, Eastern Highlands and East Sepik. In these provinces, 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 vaccines delivery. The vaccination coverage in Morobe province is equal to median vaccination coverage in PNG. In contrast, Chibu province within the analyzed period experienced a marked decline in vaccination rates – to rates lower comparing to the country average.
In PNG, there is often only one static clinic per week at the health centre level, resulting in long waiting time 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 actually 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, 13). 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 (13). The other problem is a suboptimal number of healthcare professionals. According to the official data in PNG, there are 32 paediatricians, 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 (15). 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% (16). It varies between provinces, from 30% in Jiwaka to 98% in NCD (13). In regions with the lowest use of antenatal care, the vaccination coverage provided by CHS was also low. In a study conducted by Russo in Cameroon, children born at health facilities had a higher immunization coverage rate, compared to those born at home (17). The percentage of supervised deliveries in PNG is estimated at 37% (13).
The other problem is lack of the public understanding the need for vaccinations (18,19). There are huge difficulties in communication. The adult literacy rate is estimated at 63.4% (1). So far, no negative opinions about vaccinations have been noticed in PNG, but the understanding of an idea of vaccinations is poor. For some people, there is no difference between vaccination – prevention and treatment. They view injection as a treatment. The expected benefit of participation in the survey can be raising awareness of vaccinations and their importance in protection not only for children but also for 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 huge problems in vaccination. Out of 86 health facilities,18 were severely damaged. As estimated by UNICEF, only 10% of the target population (children younger than five years) received pentavalent and MR vaccination in this province (20).
According to the National Health Information System, the measles vaccine coverage in 2016 was 51% (13). None of the provinces reported over the target 80%. The proportion of districts reporting less than 50% DTP3 (all 3 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 (21,22,23). 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.
The problem with estimation of the vaccination coverage is also caused by lack of reliable demographic data. In PNG, birth and death registration systems are not yet sufficiently developed to allow accurate estimation of a birth cohort. The population is growing very fast; hence, a real birth cohort seems to be bigger. Latest polio epidemic showed that paediatric population might be bigger than assumed. In the first round of catch-up vaccination action covering the three high-risk provinces of Morobe, Madang and Eastern Highlands, the estimated number of children was 289,582 but 303,907 (105%) children under 5 years old were vaccinated (4).
A field survey is another way to obtain the vaccination coverage. It can be done by checking patients' vaccinations records. But 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 (19). In our analysis, only 18/56 had patients had baby books; 68% had no vaccination records. Based on vaccination records, half of the patients had only one vaccination visit.
Community protection can be established by an adequate level of vaccination. Herd immunity effect is greatest when vaccination is given early in the childhood. The threshold depends on the infectiveness of the diseases and the efficacy of vaccinations. Measles is among the most highly transmissible infections. Its crude herd immunity threshold is 95%. In analysed villages, only 16 patients had profs of being vaccinated against measles and rubella. Because the efficacy of the vaccine is approximately 95%, so population coverage should be 100% (24). For polio, community protection is established at 95% of the vaccination coverage. It also depends on hygiene standards (24).
Latest polio outbreak showed lack of community protection. In Morobe and Madang provinces, the vaccination coverage in children in the first year of life was far below advised. During an outbreak, catch up vaccinations were performed. The National Health Department with the help of Provincial Health Authorities organised four round immunization campaigns from July to October 2018 to immunize children under 5 years (5). More than 5.7 million doses of OPVs had been procured for use in the vaccination campaign. This is much more than assumed based on the population number (children population under 5 years of age is around 1,000,000) (5). As a result of the recent polio campaign, 15/56 patients had proof of at least one dose of OPV.
Improving vaccination coverage in PNG is essential for outbreak control. To achieve this, it is necessary to improve the quality of services delivered by healthcare facilities and increasing community awareness of the role of vaccinations. Observed in our analysis, declining coverage rates are in accordance with data provided by GAVI, WHO and Country Official estimates. This is a very worrisome trend.