A Hidden Public Health Crisis
While the world focused intensely on COVID-19 vaccination during 2020 and 2021, another silent crisis was unfolding a sharp decline in routine, life-saving immunizations for diseases like measles, polio, and diphtheria. According to a joint report by the WHO and UNICEF in 2023, this decline marks the largest backslide in childhood immunization coverage in three decades. The consequences are becoming increasingly evident, with rising outbreaks of vaccine-preventable diseases worldwide and a pressing need to catch up on millions of missed doses.
This article delves into the scale and reasons for this decline, its clinical and policy implications, and the necessary actions to address significant unmet medical needs especially among children and underserved populations. We also explore how older and health-aware individuals adapted during this period, why vulnerable groups lagged behind, and what outcomes we can anticipate without urgent corrective action.
How Far Did Routine Vaccination Fall?
Global Coverage Statistics
According to the WHO/UNICEF Estimates of National Immunization Coverage (WUENIC, 2023), between 2019 and 2021:
- The coverage of DTP3 (diphtheria, tetanus, and pertussis vaccine) fell from 86% to 81%.
- Measles vaccine (first dose) coverage dropped from 86% to 81% globally.
- Over 25 million children missed at least one vaccine dose in 2021 alone.
- Nearly 18 million children (zero-dose children) received no routine vaccine that year, mostly in low- and middle-income countries.
These figures represent a regression to 2008 coverage levels — effectively wiping out over a decade of progress in immunization equity and access.
Country-Level Examples
- India: Reported a 6% drop in DTP3 coverage in 2020 according to WHO data, affecting over 3 million children.
- Nigeria and Ethiopia: Accounted for the highest number of zero-dose children globally.
- United States: CDC data indicated a 14% decline in kindergarten MMR (measles-mumps-rubella) vaccine coverage from 2019 to 2021.
Key Reasons for the Decline
1. Disruption of Health Services
According to WHO’s “Pulse Survey on Continuity of Essential Health Services” (2021), over 60% of countries reported disruptions in routine immunization services during the pandemic. These disruptions were due to:
- Lockdowns and movement restrictions.
- Reallocation of health workers to COVID-19 response efforts.
- Closure or reduced hours at health facilities.
- Fear of contracting COVID-19 in healthcare settings.
2. Supply Chain Interruptions
The global vaccine supply chain was severely strained. Manufacturing delays, export restrictions, and logistical bottlenecks especially affecting low-income countries led to vaccine shortages and stockouts.
3. Vaccine Hesitancy and Misinformation
The COVID-19 pandemic triggered a wave of vaccine misinformation that also affected public trust in routine childhood vaccines. A 2022 study published in Vaccine found that 38% of parents in low-income settings were hesitant to vaccinate their children during the pandemic due to misinformation about safety and side effects.
4. Inequitable Access and Digital Gaps
Increased reliance on digital platforms for health communication left behind populations without internet access or digital literacy. Poorer households and rural communities lacked access to both information and services.
Who Got Left Behind? A Disproportionate Impact
1. Children in Low- and Middle-Income Countries
Zero-dose children were overwhelmingly concentrated in conflict zones, remote rural areas, and urban slums. UNICEF reported in 2022 that 60% of unvaccinated children lived in just 10 countries, including India, Nigeria, Indonesia, and Pakistan.
2. Children from Marginalized Communities
Ethnic minorities, migrants, and indigenous groups experienced heightened vulnerability due to systemic barriers, including language, lack of documentation, and mistrust of authorities.
3. Older Adults and the 'Healthy Responder Bias'
In contrast, older adults and health-conscious individuals were more likely to pursue preventive healthcare, including COVID-19 testing and influenza vaccinations, even during the pandemic. This phenomenon often called “healthy responder bias” created a paradox where high-risk, aware individuals received more care, while the most vulnerable lacked access.
Clinical Implications: A Growing Risk of Disease Outbreaks
1. Surge in Measles and Polio Cases
- Measles: The WHO reported a 79% increase in measles cases globally in early 2022 compared to the previous year.
- Polio: Pakistan and Afghanistan reported resurgences, and outbreaks were detected in Malawi and Mozambique for the first time in decades.
These outbreaks not only threaten global eradication goals but can also overwhelm health systems already burdened by COVID-19 recovery.
2. Waning Herd Immunity
The reduced coverage compromises herd immunity thresholds, increasing the risk of community transmission of preventable diseases.
- Measles requires ~95% coverage for herd immunity.
- Diphtheria and polio require ~85–90%.
Gaps in immunization coverage can reverse decades of progress and cause localized or global health emergencies.
3. Impact on Maternal and Neonatal Health
The pandemic also disrupted maternal tetanus immunization programs. This can lead to an increase in neonatal deaths, particularly in settings lacking sterile delivery conditions.
Policy Implications: What Must Governments and Global Agencies Do?
1. Catch-Up Vaccination Campaigns
WHO recommends intensive catch-up drives, especially for children who missed scheduled doses between 2020–2022. Some successful strategies include:
- Door-to-door campaigns in India (Mission Indradhanush).
- Mass school-based immunizations in South Africa and Brazil.
- Integrated service delivery (nutrition + vaccination) to boost uptake.
2. Funding and Political Commitment
WHO estimates that an additional $2.5 billion is required globally through 2025 to restore immunization coverage to pre-pandemic levels. Donor countries, Gavi (the Vaccine Alliance), and national governments must increase allocations for immunization systems.
3. Restoring Trust Through Communication
Governments must tackle vaccine misinformation using:
- Community health workers.
- Faith-based organizations.
- Social media regulation.
- Transparent communication strategies.
UNICEF’s Communication for Development (C4D) strategy has shown success in rural Africa and South Asia in overcoming hesitancy through locally trusted messengers.
4. Strengthening Primary Healthcare
This pandemic has proven that robust primary health systems are essential for routine immunization continuity. Policy reforms should focus on:
- Training health workers.
- Improving cold-chain infrastructure.
- Ensuring supply chain resilience.
India’s Ayushman Bharat Health and Wellness Centres (AB-HWCs) and Brazil’s Family Health Strategy are examples of scalable models to integrate vaccination with general health services.
Significant Unmet Medical Needs: More Than Just Vaccines
The immunization gap reflects broader inequities in global health access. Children who missed vaccines likely also missed:
- Nutritional support (e.g., Vitamin A supplementation).
- Growth monitoring.
- Early detection of developmental delays.
These missed touchpoints have long-term implications for morbidity, mortality, and human development, particularly in the first 1,000 days of life a critical window for brain and immune system development.
Outcomes: What Happens If We Don’t Act Now?
Scenario 1: Delayed Action
If global efforts continue at the current pace:
- Vaccine-preventable disease outbreaks will persist.
- Eradication efforts (e.g., for polio) may be permanently derailed.
- Over 50 million children may remain unprotected by 2030.
- Health systems will be forced to manage preventable disease outbreaks amid climate-related and future pandemic challenges.
Scenario 2: Accelerated Response and Investment
If global partners and governments prioritize routine immunization recovery:
- By 2025, WHO estimates full recovery to pre-pandemic levels is possible.
- Up to 10 million deaths can be prevented by 2030 through immunization, according to Gavi.
- Strengthened trust in public health systems can improve readiness for future health emergencies.
Conclusion:
The COVID-19 pandemic exposed vulnerabilities in global health systems, but it also offers a once-in-a-generation opportunity to rebuild stronger, more equitable services. The collapse in routine immunization was not just a temporary setback it is a wake-up call. Millions of children are at risk, and significant unmet medical needs remain hidden beneath immunization data.
Countries must act swiftly to restore coverage, invest in resilient primary healthcare, and rebuild trust in vaccines. The catch-up effort will not be easy, but it is essential not just to regain lost ground but to build a future where every child, regardless of geography or income, has the right to live a life free from preventable diseases.
References
- WHO & UNICEF. (2023). Estimates of National Immunization Coverage (WUENIC). Retrieved from https://www.who.int
- WHO. (2021). Pulse Survey on Continuity of Essential Health Services during the COVID-19 pandemic.
- UNICEF. (2022). Immunization Catch-Up Plan: Global Strategy Brief.
- Gavi, The Vaccine Alliance. (2023). The State of Routine Immunisation Recovery.
- CDC. (2022). MMWR: Vaccination Coverage among Kindergarten Children — United States.
- Clark, A. et al. (2022). “Global estimates of children affected by COVID-19-associated orphanhood and caregiver death.” The Lancet.
- Nguyen, K. et al. (2022). “Misinformation and COVID-19 vaccine hesitancy: A global concern.” Vaccine, 40(17), 2403–2410.
