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Summary
What is already known about this topic?
High routine childhood vaccination coverage achieved during 2015–2019 declined globally for most vaccines during 2019–2021 because of COVID-19 pandemic disruptions.
What is added by this report?
In 2021, the estimated global coverage with 3 doses of diphtheria-tetanus-pertussis–containing vaccine as well as the first dose of measles-containing vaccine decreased to 81%, the lowest level since 2008. Globally, 25.0 million children were unvaccinated or incompletely vaccinated in 2021, 5.9 million more than in 2019.
What are the implications for public health practice?
Reversing declining vaccination trends and addressing immunity gaps, as well as extending previous gains in vaccination coverage beyond prepandemic levels, requires targeted and context-specific approaches that prioritize routine vaccination as an essential health service and improve access to vaccination across the life span.
In 2020, the World Health Assembly endorsed the Immunization Agenda 2030, an ambitious global immunization strategy to reduce morbidity and mortality from vaccine-preventable diseases (1). This report updates a 2020 report (2) with global, regional,* and national vaccination coverage estimates and trends through 2021. Global estimates of coverage with 3 doses of diphtheria-tetanus-pertussis–containing vaccine (DTPcv3) decreased from an average of 86% during 2015–2019 to 83% in 2020 and 81% in 2021. Worldwide in 2021, 25.0 million infants (19% of the target population) were not vaccinated with DTPcv3, 2.1 million more than in 2020 and 5.9 million more than in 2019. In 2021, the number of infants who did not receive any DTPcv dose by age 12 months (18.2 million) was 37% higher than in 2019 (13.3 million). Coverage with the first dose of measles-containing vaccine (MCV1) decreased from an average of 85% during 2015–2019 to 84% in 2020 and 81% in 2021. These are the lowest coverage levels for DTPcv3 and MCV1 since 2008. Global coverage estimates were also lower in 2021 than in 2020 and 2019 for bacillus Calmette-Guérin vaccine (BCG) as well as for the completed series of Haemophilus influenzae type b vaccine (Hib), hepatitis B vaccine (HepB), polio vaccine (Pol), and rubella-containing vaccine (RCV). The COVID-19 pandemic has resulted in disruptions to routine immunization services worldwide. Full recovery to immunization programs will require context-specific strategies to address immunization gaps by catching up missed children, prioritizing essential health services, and strengthening immunization programs to prevent outbreaks (3).
The World Health Organization (WHO) established the Expanded Programme on Immunization in 1974 to protect infants against six diseases through vaccination (e.g., BCG, DTP, Pol, and MCV) (4). Since then, additional vaccines and vaccine doses have been introduced during the first year of life (e.g., HepB, Hib, pneumococcal conjugate vaccine [PCV], RCV, and rotavirus) and at older ages (e.g., human papillomavirus [HPV] vaccine in females) (4). WHO and UNICEF produce annual estimates of immunization coverage through review of available country-specific data, including administrative and survey-based coverage†,§ (5). DTPcv3 coverage by age 12 months is an indicator of routine immunization program performance, and DTPcv3, MCV2, 3 doses of PCV (PCV3), and HPV vaccine are indicators for the Sustainable Development Goals.¶ Children who have not received any doses of DTPcv by age 12 months (zero-dose children) represent those with poor access to immunization and other essential health services. Children who receive the first DTPcv dose (DTPcv1) but do not complete the full series are considered incompletely vaccinated.
WHO and UNICEF global estimates of national immunization coverage for DTPcv1 decreased from 90% in 2019 to 87% in 2020 and 86% in 2021, the lowest level since 2005. In 2021, DTPcv1 coverage ranged from 80% in the WHO African Region to 97% in the European Region (Table 1). DTPcv3 coverage followed similar regional trends. The decline in first and third dose DTPcv coverage during 2019–2021 was largest in the South-East Asia Region (from 94% to 86% for DTPcv1 and from 91% to 82% for DTPcv3). In the Americas, DTPcv1 and DTPcv3 coverage decreased by 3 and 4 percentage points, respectively, during 2019–2021 (Figure). Among the 194 WHO member states, DTPcv1 coverage during 2019–2021 was stable or declined in 170 (88%); DTPcv3 coverage during this period was stable or declined in 167 member states (86%).
In 2021, 25.0 million children worldwide had not completed the 3-dose DTPcv series, 2.1 million more than in 2020 (22.9 million) and 5.9 million more than in 2019 (19.1 million); 18.2 million (73%) had received no doses, and 6.8 million (27%) were incompletely vaccinated with DTPcv. The number of zero-dose children was unevenly distributed by WHO region, economic classification,** and country eligibility for support from Gavi, the Vaccine Alliance (Gavi)†† (Table 2) (Figure). Among 18.2 million zero-dose children in 2021, low-income countries accounted for 5.0 million (27%), whereas middle-income countries had the largest number (12.8 million; 70%). Ten countries (43% of the global birth cohort) accounted for 62% (11.4 million) of zero-dose children: India (2.7 million), Nigeria (2.2 million), Indonesia (1.1 million), Ethiopia (1.1 million), Philippines (1.0 million), Democratic Republic of the Congo (0.73 million), Brazil (0.71 million), Pakistan (0.61 million), Angola (0.55 million), and Burma (0.49 million). Approximately 12 million zero-dose children (69% of the global total) lived in Gavi-eligible countries. DTPcv3 coverage declined sharply in 17 countries that transitioned out of Gavi support,§§ from a weighted average of 82% in 2019 to 70% in 2021, whereas those supported by Gavi were less affected (weighted average of 82% in 2019 compared with 77% in 2021).
Global MCV1 coverage remained stable during 2015–2019 (85%–86%) but decreased to 83% in 2020 and to 81% in 2021. The largest declines in MCV1 coverage during 2019–2021 occurred in the South-East Asia Region (from 94% to 86%) and the Western Pacific Region (from 95% to 91%) (Table 1). During 2015–2019, coverage with 2 MCV doses (MCV2) increased from 63% to 71%, reflecting second dose introductions in many countries.¶¶ However, MCV2 coverage remained stable thereafter (72% in 2020 and 71% in 2021), with only four additional countries introducing MCV2 during 2020–2021.
Global coverage during 2019–2021 decreased for all of the following recommended childhood vaccines: BCG, from 88% to 84%; the completed Hib series, from 73% to 71%; RCV, from 69% to 66%; 3-dose HepB series, from 85% to 80%; HepB birth dose, from 44% to 42%; and the third Pol dose, from 86% to 80%. Global coverage with first dose of HPV vaccine among females declined from 20% in 2019 to 15% in 2021, and with the last dose, from 14% in 2019 to 12% in 2021. Global PCV3 coverage was stagnant (50% in 2019, 51% in 2020, and 51% in 2021), and coverage with the final dose of rotavirus vaccine series increased from 40% in 2019 to 49% in 2021.***
Discussion
Since the start of the COVID-19 pandemic in 2020, a widespread decline in childhood vaccinations has occurred globally, putting millions of additional children at risk for vaccine-preventable diseases. Global DTPcv3 coverage declined by 5 percentage points during 2019–2021, meaning that at least 22.9 million children in 2020 and 25.0 million children in 2021 did not access or fully utilize routine immunization services. Immunization outreach services were particularly affected (6), and the most vulnerable populations have experienced the largest impact. Among all WHO regions, the largest declines in DTPcv3 and MCV1 coverage occurred in the South-East Asia Region.
The continued decline in vaccination coverage during 2020–2021 was likely a result of many factors, including strained health systems caused by the COVID-19 pandemic, coupled with delivery of COVID-19 vaccines. These stresses have led to challenges with supply chains, human resources, and financing. Increasing vaccine misinformation, disinformation, and hesitancy also likely contributed to declines in some countries (6). The risk of vaccine-preventable disease outbreaks is likely to persist if urgent action is not taken to recover immunization program losses.
Expanding immunization services to reach zero-dose and incompletely vaccinated children and reducing immunization inequities are key objectives of the Immunization Agenda 2030 (1). Gavi has provided support for vaccines and vaccination services to low- and lower-middle income countries since 2000, helping to improve access and reduce disparities in immunization coverage with high-income countries (7). However, during 2019–2021, vaccination coverage declined more sharply in countries that transitioned out of Gavi support than in those supported by Gavi, underscoring the vulnerability of these systems. As countries develop economically, they potentially become less eligible for external funding and require increased domestic financing for immunization. In times of crisis, such as during the COVID-19 pandemic, middle-income countries, which account for an increasing share of unprotected children, might be unable to allocate sufficient resources to immunization programs to reach every child with available vaccines.
The findings in this report are subject to at least five limitations. First, for 18 countries (6% of the global birth cohort) that did not report immunization coverage data for 2021 by July 7, 2022, estimated coverage for 2020 was used.††† Second, because COVID-19 also disrupted survey implementation, estimates for 2021 are less determined by survey data than are estimates for previous years. Third, the estimated numbers of zero-dose and incompletely vaccinated children rely on population estimates that are subject to inaccuracies. Fourth, data quality limitations in some countries might have resulted in inaccurate estimates of administrative coverage, and selection and recall bias could affect survey-based estimates of coverage (5). Finally, coverage estimates do not include statistical uncertainty.
Reversing worrisome vaccination trends and extending previous gains in coverage beyond prepandemic levels will require targeted and context-specific approaches to eliminate barriers to vaccination, particularly in communities with large populations of zero-dose children. WHO has published strategies and guiding principles for implementing catch-up vaccination and recovering essential immunization services (8–10). Countries are urged to recover immunization services while capitalizing on opportunities from the pandemic response and COVID-19 vaccine rollout to strengthen routine immunization services and increase primary health care resiliency. This can be achieved by prioritizing routine immunization as an essential health service, improving access to vaccination across the life span, strengthening data systems, safeguarding sustainable immunization financing, and building vaccine confidence.
1Epidemic Intelligence Service, CDC; 2Global Immunization Division, Center for Global Health, CDC; 3Department of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland; 4Division of Data, Analytics, Planning and Monitoring, UNICEF, New York, New York.
Source of original article: Centers for Disease Control and Prevention (CDC) / Morbidity and Mortality Weekly Report (MMWR) (tools.cdc.gov).
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