The negative impact of the COVID-19 Pandemic on immunization and the positive impact on Polio eradication in Pakistan and Afghanistan

Dear Editor,

In a recent letter by Usman Ayub Awan et al. [1]., the authors described the outbreak of the wild poliovirus in Afghanistan. We agree with the concerns raised by the authors and here we would like to discuss the current polio situation and the impact of the COVID-19 pandemic on polio vaccination in Pakistan and Afghanistan.

The global polio eradication initiative was launched in 1988, when the wild poliovirus was endemic in 125 countries, paralyzing 350,000 individuals per year. Enormous progress has been made towards the eradication of polio by reducing 99% of global incidence due to immunization efforts [2].

Vaccines and the importance of immunization have taken center stage in public discourse like never before. As the world focus on COVID-19 Vaccination campaigns, what does this mean for other vaccine-preventable diseases such as polio? The covid-19 pandemic has compromised public health systems around the world and disrupted the delivery of essential health services including efforts to achieve polio eradication. The three-decades-long derive to eradicate polio was going back even before COVID-19 hit, and the pandemic has made a bad situation worse. In 2019 and 2020, cases of wild poliovirus rose in Pakistan and Afghanistan, the last two countries where it is endemic.

The ongoing COVID-19 Pandemic is disrupting life-saving immunization services globally, but with a particular impact in low-income countries including Pakistan and Afghanistan. The highest number of unimmunized children live in south Asia, with 97% of them living in Pakistan, Afghanistan, and India [3]. The evidence from previous Ebola epidemics has demonstrated that even temporary interruptions of routine immunization services can lead to secondary public health crises such as outbreaks of vaccine-preventable diseases including polio and measles.

Pakistan and Afghanistan are the fifth and thirty-seventh most populous countries in the world. Both countries spend less than 1% of their gross domestic product on health services. Owing to the low investment in the health sector many vaccines preventable diseases (VPDs) are still endemic in Pakistan and Afghanistan including polio and measles. The polio eradication program in Pakistan and Afghanistan successfully reduces the number of confirmed polio cases from 306 in 2014 to only 12 in 2018 in Pakistan and from 28 cases in 2014 to 21 cases in 2018 in Afghanistan. Unfortunately, there was a resurgence of polio cases to 147 in 2019 and 84 polio cases in 2020 were reported in Pakistan. Similarly, 29 polio cases in 2019 and 56 in 2020 were reported in Afghanistan. Surprisingly, in the presence of millions of unimmunized children, only one polio case was reported in Pakistan and 4 polio cases were reported in Afghanistan in 2021. Only one polio case is reported in Afghanistan and zero polio cases in Pakistan in 2022. From 2010-to 2022, a total of 1122 and 342 polio cases were reported from Pakistan and Afghanistan respectively. Detail of reported polio cases in Pakistan and Afghanistan is given in Fig. 1 .

Fig. 1.

Reported polio cases 2010–2022 in Pakistan and Afghanistan.

The coverage of routine immunization including polio and measles vaccination in Pakistan and Afghanistan is far lower than the 90% that is required for herd immunity and immunization against polio has further declined by 50% during the COVID-19 pandemic when 50 million children in Pakistan [3] and 23 million children in Afghanistan [4] did not receive a polio vaccination owing to the suspension of immunization activities. Before the COVID-19 pandemic, more than 600,000 Afghan children miss polio vaccination because of the refusal of their parents [5]. There is an 18,593 live birth average per day in Pakistan and a 3986 live birth average per day in Afghanistan, the suspension of door-to-door polio immunization campaigns has left a huge and growing pool of children who are susceptible to polio in both countries. When the virus finds them, it will tear through the unimmunized population and may lead to more polio outbreaks in near future. Recently polio outbreak has been declared in Malawi, the poliovirus strain found in the child in Lilongwe has been linked to one circulating in Pakistan [6].

Due to the disruption in immunization, the crystal-clear evidence of the unprecedented upsurge in vaccine-preventable diseases such as measles in Pakistan and Afghanistan resulted in 28,125 suspected measles cases, including 800 deaths reported from Pakistan [7] and 35,300 suspected measles cases including 156 deaths were reported from Afghanistan in 2021. Most other VPDs such as Diphtheria, Pertussis, typhoid, TB, Hepatitis, Rota, and Rubella virus are on the rise due to the disruption in immunization owing to a pandemic, but poliovirus is unprecedently declined in both countries.

Multiple hurdles in polio eradication are still there in both countries such as poor immunization coverage, vaccine hesitancy, vaccine refusal, conspiracy theories, political instability, overcrowded population, killing of polio workers, population movement, remote locations, and conflict. In the presence of multiple hurdles fueled by the COVID-19 pandemic, the more than 99% decline in polio cases in Pakistan and Afghanistan is difficult to understand for the scientific community. The sudden absence of polio circulation is a daunting task that cannot be verified reliably because of the limitations of existing surveillance tools, which include acute flaccid paralysis surveillance supplemented by environmental surveillance. In a fully susceptible population, acute flaccid paralysis surveillance can detect one in 100 to 1000 infections. However, with increasing population immunity, surveillance for clinical signs of poliovirus infection become much less sensitive, allowing poliovirus to circulate undetected for many years. If the decline in polio cases in Pakistan and Afghanistan is due to the vaccination campaigns, now the key is to prevent a resurgence in the coming peak season for polio transmission in both countries.

World Health Organization and patterners in the global polio eradication initiative are committed to fully supporting the government of Pakistan and Afghanistan to tackle polio in its last strongholds and failure to eradicate polio now could result in a resurgence of the disease, with as many as 200,000–300,000 new cases worldwide every year.

Although Pakistan and Afghanistan face distinct polio eradication challenges, they are linked epidemiologically because of high rates of cross-border population movement. Transit-point vaccination must be maintained as emigration from Afghanistan potentially increases after the Taliban control.

The persistence of polio in Pakistan and Afghanistan, and the increase in circulating vaccine-derived poliovirus, has been a warning call for intensifying efforts for control despite the disruption imposed by the COVID-19 pandemic. Disruption in immunization in both countries coupled with Taliban rule in Afghanistan threatens to reverse significant achievements in polio eradication and the world must seek innovative approaches to work with the Taliban to get polio and other VPDs under control.

The COVID-19 pandemic is a magnifying glass that has highlighted the larger threat of existing public health challenges such as polio. The long-term trajectory of the pandemic is uncertain, and the risk of resurgence of epidemic-prone diseases including polio is very high. Additionally, at the same time, the health system's capacity to perform a meaningful epidemiological analysis of the situation may also be impacted. Pakistan and Afghanistan are already struggling to eradicate polio and disruption in immunization owing to the pandemic the risk of polio outbreak is on the brink and it may provide the virus a milieu to spread further and faster and could also result in the worldwide spread of polio infection. The world cannot afford to have another epidemic of polio after the devastating impact of the COVID-19 pandemic.