Analysis of global routine immunisation coverage shows disruption and stagnation during the first two-years of the COVID-19 pandemic with tentative recovery in 2022

Abstract

Whilst it is now widely recognised that routine immunisation (RI) was disrupted by the COVID-19 pandemic in 2020, and further so in 2021, the extent of continued interruptions in 2022 and/or rebounds to previous trends remains unclear. We modelled country-specific RI trends using validated estimates of national coverage from the World Health Organisation and United Nation Children's Fund for 182 countries (accounting for > 97% of children globally), to project expected diphtheria, tetanus, and pertussis-containing vaccine first-dose (DTP1), third-dose (DTP3) and measles-containing vaccine first-dose (MCV1) coverage for 2020-2022 based on pre-pandemic trends (from 2000 to 2019). We provide further evidence of peak pandemic immunisation disruption in 2021, followed by tentative recovery in 2022. We report a 3.4% (95 %CI: [2.5%; 4.4%]) decline in global DTP3 coverage in 2021 compared to 2000-2019 trends, from an expected 89.8% to reported 86.4%. This coverage gap reduced to a 2.7% (95 %CI: [1.8%; 3.6%]) decline in 2022, with reported coverage rising to 87.2%. Similar results were seen for DTP1 and MCV1. Whilst partial rebounds are encouraging, global coverage decline translates to a 17-year setback in RI to 2005 levels, and the majority of countries retain coverage at or lower than pre-pandemic levels. The Americas, Africa, and Asia were the most impacted regions; and low- and middle-income countries the most affected income groups. The number of annual Zero Dose (ZD) children - indicating those receiving no immunisations - increased from 12.1 million (M) globally in 2019 to a peak of 16.7 M in 2021, then reduced to 13.1 M in 2022. Overall, we estimate an excess of 8.8 M ZD children cumulatively in 2020-2022 compared to pre-pandemic levels. This work can be used as an objective baseline to inform future interventions to prioritise and target interventions, and facilitate catch-up of growing populations of under- and un-immunised children.

Keywords: COVID-19; Coverage; Decline; Global; Global health; Immunisation; Modelling; Pandemic; Recovery; Routine immunisation; Time series; Vaccine.

Fig. 1

Example modelling outputs for five largest countries: Expected (2020–2022) and reported (2000–2022) vaccine coverage for DTP1 (panel A), DTP3 (panel B), and MCV1 (panel C) for 2000–2022. These graphs show WUENIC-reported coverage data (black dots), and the corresponding ARIMA predictions and the associated 95% Confidence Intervals (red bars). DTP1 = diphtheria, tetanus, and pertussis-containing vaccine first-dose, DTP3 = diphtheria, tetanus, and pertussis-containing vaccine third-dose, MCV1 = measles-containing-vaccine first-dose. ARIMA = AutoRegressive Integrated Moving Average modelling. WUENIC = WHO/UNICEF Estimates of National Immunization Coverage. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Global trends in DTP1 (orange), DTP3 (yellow), and MCV1 (blue) coverage over time. Expected (dotted line) refers to ARIMA-forecast coverage levels. WUENIC-reported data (solid line) is lower than expected coverage during the pandemic from 2020 to 2022. Horizontal and vertical dashed yellow lines compare reported DTP3 2022 coverage to year coverage levels last seen. DTP1 = diphtheria, tetanus, and pertussis-containing vaccine first-dose, DTP3 = diphtheria, tetanus, and pertussis-containing vaccine third-dose, MCV1 = measles-containing-vaccine first-dose. ARIMA = AutoRegressive Integrated Moving Average modelling. WUENIC = WHO/UNICEF Estimates of National Immunization Coverage. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Differences between expected and reported DTP3 vaccine coverage in 2020–2022 by region and income groups. Points represent individual countries, grouped, and coloured according to (panels A, C & E) region classification and (B, D & F) World Bank income groups, over 2020 (panels A & B), 2021 (panels C & D), and 2022 (panels E & F). Country coordinates on the X-axis were jittered for visibility. Values on the y-axis are indicated as absolute differences between reported and expected vaccine coverage, in percentages. Violin plots show the density of the data within each group: wider lines indicate more datapoints. The black dashed horizontal lines indicate no change in coverage. LIC: Low-income Country. LMIC: Lower-middle-income Country. UMIC: Upper-middle-income Country. HIC: High-income Country. DTP3 = diphtheria, tetanus, and pertussis-containing vaccine third-dose.

Fig. 4

Comparison between WUENIC-reported DTP3 coverage and expectations derived from historical trends: This scatterplot shows country coverage (WUENIC-reported actuals and ARIMA-predicted expectations) as dots for 2020 (panel A), 2021 (panel B) and 2022 (panel C). Lines around individual points illustrate the 95% Confidence Intervals (CIs) of ARIMA predictions. Countries showing significant departure from expected values, i.e., for which actual coverage is outside the 95% CI of predictions, are indicated in red; countries without such significant departure from expected results are shown in black. Countries with reported coverage lower than expected coverage are on the right-hand side of the dotted diagonal line. DTP3 = diphtheria, tetanus, and pertussis-containing vaccine third-dose. ARIMA = AutoRegressive Integrated Moving Average modelling. WUENIC = WHO/UNICEF Estimates of National Immunization Coverage. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Classification of pandemic impact and recovery by country for DTP3: This scatterplot shows the combined 3-year (2020–2022) delta between expected and reported coverage on the x-axis and absolute difference between reported coverage in 2022 and 2019 on the y-axis. Labelling describes and quantifies (total and percentage of 182 countries) country classification with respect to the two plotted dimensions. DTP3 = diphtheria, tetanus, and pertussis-containing vaccine third-dose.

Fig. 6

Number of Zero Dose (ZD) children per year from 2000 to 2022: panel A shows the global total with a dotted line indicating 2019 ZD levels; panel B breaks down the total by region and panel C by income group.