Epidemiology of polio virus infection in Pakistan and possible risk factors for its transmission

Vaccine Hesitancy: Contemporary Issues and Historical Background

Vaccination, despite being recognized as one of the most effective primary public health measures, is viewed as unsafe and unnecessary by an increasing number of individuals. Anxiety about vaccines and vaccination programs leading to vaccine hesitancy results from a complex mix of social and political influences, cultural and religious beliefs, the availability of and ability to interpret health and scientific information, and personal and population experiences of health systems and government policies. Vaccine hesitancy is becoming a serious threat to vaccination programs, and was identified as one of the World Health Organization’s top ten global health threats in 2019. The negative impact of anti-vaccination movements is frequently cited as one of the major reasons for rising vaccine hesitancy amongst the general public world-wide. This review discusses the various issues surrounding vaccine hesitancy and the anti-vaccine movement, starting with the definitions of vaccine hesitancy and the anti-vaccine movement in their early history and in the modern era, before discussing the key drivers of vaccine hesitancy, particularly across different regions of the world, with a focus on various countries with low-, middle-, or high-income economies with different socio-economic populations. The review concludes with the impact of vaccine hesitancy on herd immunity and social, psychological, and public health measures to counter vaccine hesitancy.

Attitude and perception towards vaccination against poliomyelitis in Peshawar, Pakistan

OBJECTIVE:

This research aimed to quantitatively assess the general public's awareness, attitude and perception of polio and its vaccination in Peshawar KPK, Pakistan.

METHODS:

We conducted a survey-based study to understand the surge in polio cases from 2015 to 2019 in the Peshawar city of the Khyber Pakhtunkhwa (KPK), Pakistan. A pre-tested questionnaire-based study was conducted in 2019 to assess the attitude and general perception of residents of Peshawar KPK towards polio vaccination.

RESULTS:

Out of 241 country-wide polio cases, 63 (26.1%) polio cases were reported in Peshawar city from 2015–2019. The questionnaire revealed that individuals between 18–30 years of age had sufficient knowledge (65.1%) about polio. Male and female participants had equal awareness (~ 43%). Participants with higher education (45.9%), those with better financial status (49.5%), individuals with children < 5 years of age (46.4%), and those who had experience of a polio patient (63.1%) had better knowledge. Participants inhabiting the central city were better aware (50.5%) of polio than individuals living in the outskirts.

CONCLUSION:

The data indicated that poor knowledge and negative attitudes of people towards polio vaccination are the main causes of the polio eradication program's failure. Moreover, religious beliefs, unchecked migration between the Pak-Afghan border, and lack of knowledge about polio vaccination are identified as critical barriers to polio eradication.

Genetic Epidemiology Reveals 3 Chronic Reservoir Areas With Recurrent Population Mobility Challenging Poliovirus Eradication in Pakistan

BACKGROUND

Pakistan is among 3 countries endemic for wild poliovirus type 1 (WPV1) circulation that are still struggling for eradication of poliomyelitis. Active clinical and environmental surveillance with meticulous laboratory investigations provide insights into poliovirus transmission patterns and genomic diversity to inform decisions for strategic operations required to achieve eradication.

METHODS

We analyzed epidemiological and virological data to comprehend the current epidemiological status of WPV1 in Pakistan during 2015-2017. Stool specimens of patients with acute flaccid paralysis (AFP) and sewage samples collected from 60 environmental sites were tested. Viral culturing, intratypic differentiation by real-time polymerase chain reaction, and nucleic acid sequencing of the VP1 region of the poliovirus genome to determine genetic relatedness among WPV1 strains were applied.

RESULTS

Poliovirus isolates were grouped into 11 distinct clusters, which had ≥95% nucleotide homology in the VP1 coding region. Most of the poliovirus burden was shared by 3 major reservoirs: Karachi, Peshawar, and Quetta block (64.2% in 2015, 75.4% in 2016, and 76.7% in 2017).

CONCLUSIONS

Environmental surveillance reveals importations and pockets of unimmunized children that dictate intensive target mop-up campaigns to contain poliovirus transmission. A decrease in the number of orphan isolates reflects effective combination of AFP and environmental surveillance in Pakistan. The genetic data reflect sustained transmission within reservoir areas, further expanded by periodic importations to areas of high immunity reflected by immediate termination of imported viruses. Improved immunization coverage with high-quality surveillance is vital for global certification of polio eradication.

Spatiotemporal clustering analysis of Expanded Program on Immunization (EPI) vaccination coverage in Pakistan

Universal vaccination coverage is still far from desired targets in many global regions including Pakistan, despite the success stories and its scientifically proven benefits. EPI Pakistan vaccination coverage data 2012–2016, at district level was collected from Federal EPI Pakistan. District-wise population data were collected from Pakistan Bureau of Statistics. Descriptive statistics and sequence plots were performed in SPSS 13.0. Purely spatial scanning analysis was done in SaTScan 9.4.4 using discrete Poisson model for detection of low vaccination coverage clusters. Geographical information system (GIS) was used to display spatial patterns and clusters of low vaccination coverage districts in Pakistan. Average annual EPI vaccination coverage in each study year were; 70.98 in 2012, 69.39% in 2013, 66.74% in 2014, 61.47% in 2015, and 67.01% in 2016, respectively. Cumulative average national vaccination rate (2012–2016) for all types of EPI vaccines was 60.60%. Average national vaccination rate for BCG, OPV3, pentavalent3 and measles1 was 67.12%, 58.53%, 58.47%, and 58.29%, respectively. Spatial cluster analysis demonstrated that most of low coverage districts for BCG, OPV3 and pentavalent3 were from FATA and KPK; while measles1 low coverage districts belonged to Balochistan. Future research should probe factors involved in low vaccination coverage in high risk districts.

Comparative epidemiology of poliovirus transmission

Understanding the determinants of polio transmission and its large-scale epidemiology remains a public health priority. Despite a 99% reduction in annual wild poliovirus (WPV) cases since 1988, tackling the last 1% has proven difficult. We identified key covariates of geographical variation in polio transmission patterns by relating country-specific annual disease incidence to demographic, socio-economic and environmental factors. We assessed the relative contributions of these variables to the performance of computer-generated models for predicting polio transmission. We also examined the effect of spatial coupling on the polio extinction frequency in islands relative to larger land masses. Access to sanitation, population density, forest cover and routine vaccination coverage were the strongest predictors of polio incidence, however their relative effect sizes were inconsistent geographically. The effect of climate variables on polio incidence was negligible, indicating that a climate effect is not identifiable at the annual scale, suggesting a role for climate in shaping the transmission seasonality rather than intensity. We found polio fadeout frequency to depend on both population size and demography, which should therefore be considered in policies aimed at extinction. Our comparative epidemiological approach highlights the heterogeneity among polio transmission determinants. Recognition of this variation is important for the maintenance of population immunity in a post-polio era.