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International Health

April 6, 2021

Mass COVID-19 Vaccination Campaigns Could Impede Routine Health Services in Resource-Constrained Settings if Precautions are Not Taken, New Study Finds

A new analysis found that frequent mass vaccination campaigns conducted in Nigeria were associated with a decrease in completion of routine immunizations for children under five, maternal health care utilization, and post-birth child survival rates. The study found that during the study period, from October 2000 to December 2017, mass vaccination campaigns led to potentially 3.6 million children failing to be fully immunized in the country. The study was conducted by researchers at the Johns Hopkins Bloomberg School of Public Health and the University of Warwick School of Cross-Faculty Studies. The findings have implications for future global health initiatives that aim to control infectious diseases using mass vaccination campaigns, including COVID-19, in areas with resource-constrained health systems.

Polio vaccine

Published in BMJ Global Health on March 8, 2021, the study aimed to understand whether and how mass vaccination campaigns support or damage the services provided by country health systems. The researchers conducted an analysis of polio eradication campaigns in Nigeria enacted as part of the Global Polio Eradication Initiative (GPEI), a global multibillion dollar effort to eradicate polio led by national governments with six partners—the WHO, Rotary International, the CDC, UNICEF, the Bill & Melinda Gates Foundation, and Gavi, the Vaccine Alliance. 

Mass vaccination campaigns are a key strategy in global health initiatives to provide life-saving interventions in times of emergencies and prevent rapid spread of a disease. They are often used in countries and areas with weaker health systems in order to bypass health service provision bottlenecks and are often designed in parallel to the health system, instead of incorporated into routine immunization services where children typically receive their full schedule of vaccinations. For this study, children are considered fully immunized if they complete the full schedule of three doses of DPT vaccine, one dose of Bacillus Calmette-Guerin (BCG) vaccine, and one dose of the measles vaccine. The polio vaccine is not included in routine immunization services for this study. 

By using information on mass vaccination dates and locations, researchers were able to calculate the number of campaign rounds to which children and pregnant women were exposed. They then used data from Demographic and Health Surveys (DHS) conducted in Nigeria from 2000 to 2017 to assess the effect of these mass vaccinations on three health outcomes: full childhood immunization completion, maternal health care utilization, and child survival. 

Over the period from October 2000 to December 2017, the total number of mass vaccination campaigns ranged from 45 to 120 per local government area of Nigeria. The study found that, between 2000 and 2017, each mass vaccination campaign conducted for polio vaccination was associated with between 41,700 and 127,500 Nigerian children not being fully immunized. Over the entire study period, this translates into lost opportunities to fully immunize more than 3.6 million children.  

“This study highlights the importance of strengthening routine immunization, and integrating mass vaccination campaigns in routine immunization systems,” says Olakunle Alonge, MD, PhD ’13, MPH ’09, assistant professor in the Department of International Health at the Bloomberg School and lead author of the study.

Nigeria was the most recent country to be declared polio-free, but its path to get there and sustain its polio-free status has been challenging. The country has frequently employed mass polio vaccination campaigns as part of the GPEI strategy, similar to other countries with resource-constrained health systems. These campaigns are multi-day events where oral polio vaccine is delivered both at fixed sites and door-to-door, with the aim of achieving high coverage among children under the age of five. Nigeria is divided into six areas and the health system is decentralized along three tiers: federal, state, and local government areas. Significant variations in health systems performance exist across these regions. The mass vaccination campaigns are nationwide; however, areas with polio transmission—typically the regions with relatively poorer health systems performance—are targeted with many subnational campaigns in addition to the nationwide campaigns, resulting in more frequent exposure to the mass vaccination campaigns than areas that are only exposed to the nationwide campaigns. 

The study found that the more vaccination campaigns a population was exposed to, the lower percentage of children would achieve full routine immunization coverage, independent of health systems factors (accounted for by measuring variation in coverage due to differences in the strength of health systems across local government areas). In addition to lower full vaccination coverage, mass vaccination campaigns were also associated with a 0.9% reduction in child survival rates for every 10 mass vaccination campaigns—including pre-birth and post-birth child survival—and a reduction in maternal health care utilization, such as the number of antenatal care visits, tetanus toxoid injections prior to birth, and health facility births.

In areas with weak health systems and low full immunization coverage across the world, the GPEI made a strategic decision to increase the number of campaigns, rather than using funding to support routine immunization services. This study showed that weak health systems are particularly vulnerable to disruptions from mass vaccination programs and that large numbers of campaigns in weak health system contexts may strain limited health systems resources. Areas with weaker health systems performance often experienced a shutdown of other health care services while the mass polio vaccination campaigns were conducted, suggesting the campaigns further eroded already weak health systems. The study authors also note that mass campaigns can also lead to distrust in the health care system by the local population, in cases where campaigns are well-funded and where the health system lacks basic resources. This discrepancy can undermine people’s confidence in the quality of the services they are receiving.

In contrast, areas in Nigeria with better health systems performance had fewer mass vaccination campaigns and experienced beneficial effects on maternal health services. Stronger health systems are more able to take advantage of added resources that mass campaigns provide, such as financial resources and physical capital to support health workers in addressing non-polio health services needs.

While a mass vaccination campaign is an important strategy to control infectious diseases, there is potential for detrimental side effects if the campaigns are not also working to strengthen health systems in resource-constrained settings. In order to mitigate the potential negative effects of a mass COVID-19 vaccination program, the data suggests campaigns should actively harmonize implementation plans and service delivery between a mass vaccination campaign and routine health services. The study authors encourage governments, multilateral organizations, and NGOs seeking to implement a similar global eradication intiative for other diseases, including COVID-19, to develop context-specific plans at the national and subnational levels prior to vaccine rollout. 

Impact and effect mechanisms of mass campaigns in resource-constrained health systems: quasi-experimental evidence from polio eradication in Nigeria was written by Alonge, Marco Haenssgen, DPhil, MPhil, assistant professor in the Department of Global Sustainable Development, School of Cross-Faculty Studies, University of Warwick, UK; and Svea Closser, PhD, MPH, associate professor in the Department of International Health at the Bloomberg School. 

The publication was funded under the Synthesis and Translation of Research and Innovations from Polio Eradication (STRIPE) project, by the Bill & Melinda Gates Foundation.