The COVID-19 burden in the globe
On a global scale, COVID-19 has seen a significant surge in the number of incident cases, climbing from 1.626 million (95%UI 1.554 to 1.693) in 2020 to 2.280 million (95%UI 2.181 to 2.372) in 2021(Table 1). The age-standardized incidence rate (ASIR) of COVID-19 rose from 20,820 (95%UI 19,910 to 21,680) in 2020 to 28,960 (95%UI 27,710 to 30,140) in 2021 (Table 1). This upward trend is also evident in the disability-adjusted life years (DALYs), which increased from 12.34 million (95%UI 11.65 to 13.27) in 2020 to 21.20 million (95%UI 19.79 to 23.47) in 2021 (Table 2), and in the number of deaths, which jumped from 0.48 million (95%UI 0.46 to 0.51) to 0.79 million (95%UI 0.75 to 0.84) (Table 3). The ASRs of DALYs and deaths (ASDR) also witnessed an increase from 1482.05 (95% UI 1399.13 to 1594.52) in 2020 to 2500.65 (95% UI 2330.24 to 2778.19) and from 58.68 (95% UI 55.84 to 62.36) to 93.97 (95% UI 89.47 to 100.05) in 2021, respectively. Collectively, these data underscore a pronounced global increase in the burden of COVID-19 from 2020 to 2021.
Table 1
The incidence of COVID-19 in 2020 and 2021
Characteristics | 2020 | | 2021 |
Incidence No×105(95% CI) | | ASIR/105 No. (95% CI) | | Incidence No×105 (95% CI) | | ASIR/105 No. (95% CI) |
Overall | 16255.31(15542.07 ~ 16932.09) | | 20819.83(19907.96 ~ 21681.49) | | 22797.18(21813.59 ~ 23724.6) | | 28955.3(27708.34 ~ 30143.22) |
Sex | | | | | | | |
Male | 8132.81(7774.45 ~ 8471.9) | | 20662.94(19753.98 ~ 21523.7) | | 11391.24(10898.56 ~ 11860.76) | | 28699.17(27460.54 ~ 29886.84) |
Female | 8122.5(7768.23 ~ 8458.4) | | 20982.17(20066.83 ~ 21849.04) | | 11405.94(10917.05 ~ 11863.84) | | 29212.84(27953.58 ~ 30402.13) |
Socio-demographic factor | | | | | | | |
High SDI | 1182.07(1127.71 ~ 1247.34) | | 11177.5(10658.3 ~ 11801.11) | | 1516.04(1459.56 ~ 1576.12) | | 14187.89(13649.3 ~ 14766.99) |
High-middle SDI | 1604.26(1453.72 ~ 1791.1) | | 12208.45(11037.69 ~ 13639.29) | | 2683.5(2478.05 ~ 2892.52) | | 20548.63(19028.63 ~ 22158.1) |
Middle SDI | 4192.71(3979.63 ~ 4405.93) | | 17223.84(16341.51 ~ 18099.36) | | 5935.7(5620.43 ~ 6240.46) | | 24293.65(23013.88 ~ 25540.23) |
Low-middle SDI | 5836.8(5243.32 ~ 6358.34) | | 30418.58(27315.11 ~ 33129.75) | | 7833.24(7069.98 ~ 8628.43) | | 40191.01(36265.81 ~ 44239.52) |
Low SDI | 3428.83(3155.51 ~ 3671.99) | | 32146.11(29566.51 ~ 34502.49) | | 4808.2(4362.82 ~ 5179.69) | | 44162.31(39935.34 ~ 47666.3) |
Health System | | | | | | | |
Advanced Health System | 2418.76(2264.19 ~ 2613.53) | | 15882.22(14853.25 ~ 17182.31) | | 3505.54(3308.2 ~ 3692.03) | | 22880.72(21582.27 ~ 24115.8) |
Basic Health System | 4059.82(3643.45 ~ 4309.75) | | 13232.01(11841.31 ~ 14060.27) | | 5845.92(5426.4 ~ 6206.37) | | 19093.77(17694.71 ~ 20270.59) |
Limited Health System | 8624.35(8081.62 ~ 9204.53) | | 30074.43(28173.88 ~ 32126.36) | | 12128.61(11278.29 ~ 12967.96) | | 41612.64(38673.38 ~ 44478.07) |
Minimal Health System | 1141.74(949.36 ~ 1264.84) | | 37138.85(30739.08 ~ 41176.27) | | 1296.61(1131.2 ~ 1465.27) | | 40673.31(35418.59 ~ 46010.21) |
Table 2
The DALYs of COVID-19 in 2020 and 2021
Characteristics | 2020 | | 2021 |
DALYs No×105(95% CI) | | Age standardized DALYs/105 No. (95% CI) | | DALYs No×105 (95% CI) | | Age standardized DALYs/105 No. (95% CI) |
Overall | 1233.53(1164.95 ~ 1326.67) | | 1482.05(1399.13 ~ 1594.52) | | 2120.1(1979.42 ~ 2346.74) | | 2500.65(2330.24 ~ 2778.19) |
Sex | | | | | | | |
Male | 785.34(742.05 ~ 842.84) | | 1978.69(1870.47 ~ 2122.5) | | 1317.73(1241.18 ~ 1427.12) | | 3247.63(3059.78 ~ 3519.11) |
Female | 448.19(417.85 ~ 493.7) | | 1033.11(960.27 ~ 1145.4) | | 802.37(731.19 ~ 925.2) | | 1822.51(1651.07 ~ 2127.48) |
Socio-demographic factor | | | | | | | |
High SDI | 165.98(159.33 ~ 172.46) | | 970.57(928.41 ~ 1017.45) | | 209.73(199.76 ~ 224.6) | | 1220.09(1147.78 ~ 1340.75) |
High-middle SDI | 151.92(139.08 ~ 165.84) | | 831.29(759.4 ~ 908.58) | | 316.22(286.06 ~ 348.33) | | 1709.48(1538.74 ~ 1903.02) |
Middle SDI | 333.73(307.03 ~ 369.93) | | 1279.9(1178.04 ~ 1418.43) | | 621(567.99 ~ 703.32) | | 2328.92(2130.75 ~ 2637.67) |
Low-middle SDI | 388.21(360.23 ~ 423.11) | | 2601.57(2417.42 ~ 2807.41) | | 634.22(581.47 ~ 711.9) | | 4123.04(3819.54 ~ 4558.85) |
Low SDI | 192.73(178.85 ~ 210.41) | | 3346.64(3132.89 ~ 3626.09) | | 336.51(308.71 ~ 382.25) | | 5646.42(5245.88 ~ 6168.2) |
Health System | 0(0 ~ 0) | | 0(0 ~ 0) | | 0(0 ~ 0) | | 0(0 ~ 0) |
Advanced Health System | 284.54(269.71 ~ 299.48) | | 1178.94(1113.66 ~ 1251.86) | | 458.64(425.75 ~ 496.8) | | 1894.32(1740.35 ~ 2107.67) |
Basic Health System | 361.73(325.63 ~ 412.15) | | 1014.09(912.31 ~ 1154.64) | | 666.68(599.32 ~ 765.8) | | 1834.52(1644.46 ~ 2116.02) |
Limited Health System | 521.01(486.35 ~ 565.94) | | 2497.51(2339.81 ~ 2685.32) | | 890.02(824.6 ~ 997.97) | | 4133.55(3877.05 ~ 4515.22) |
Minimal Health System | 65.29(58.15 ~ 72.76) | | 4395.43(3951.86 ~ 4860.26) | | 102.34(92.4 ~ 115.15) | | 6612.23(5958.95 ~ 7230.39) |
Table 3
The deaths of COVID-19 in 2020 and 2021
Characteristics | 2020 | | 2021 |
Death No×105 (95% CI) | | ASDR/105 No. (95% CI) | | Death No×105 (95% CI) | | ASDR/105 No. (95% CI) |
Overall | 48.02(45.67 ~ 51.06) | | 58.68(55.84 ~ 62.36) | | 78.88(75.07~)84.04 | | 93.97(89.47 ~ 100.05) |
Sex | | | | | | | |
Male | 29.67(28.1 ~ 31.66) | | 80.39(76.22 ~ 85.61) | | 48.04(45.54~)51.37 | | 126.36(119.88 ~ 134.85) |
Female | 18.35(17.44 ~ 19.48) | | 40.8(38.78 ~ 43.33) | | 30.83(29.15~)32.77 | | 67.07(63.42 ~ 71.3) |
Socio-demographic factor | | | | | | | |
High SDI | 7.97(7.68 ~ 8.24) | | 38.02(36.65 ~ 39.31) | | 9.77(9.46~)10.15 | | 45.84(44.39 ~ 47.59) |
High-middle SDI | 7.09(6.52 ~ 7.73) | | 37.93(34.91 ~ 41.36) | | 13.8(12.72~)14.85 | | 71.68(66.05 ~ 77.08) |
Middle SDI | 12.6(11.64 ~ 13.91) | | 52.21(48.2 ~ 57.63) | | 22.57(20.87~)25.14 | | 90.93(84.2 ~ 101.29) |
Low-middle SDI | 14.02(13.13 ~ 14.95) | | 110.21(103.29 ~ 117.49) | | 22(20.74~)23.74 | | 168.71(159.29 ~ 181.78) |
Low SDI | 6.3(5.96 ~ 6.77) | | 145.97(138.16 ~ 156.68) | | 10.63(9.97~)11.27 | | 242.08(227.27 ~ 256.33) |
Health System | | | | | | | |
Advanced Health System | 13.69(13.08 ~ 14.39) | | 47.5(45.31 ~ 49.9) | | 20.96(19.82~)22.11 | | 72.36(68.29 ~ 76.5) |
Basic Health System | 13.9(12.48 ~ 15.88) | | 41.3(37.16 ~ 47.07) | | 24.54(22.28~)28.17 | | 70.81(64.46 ~ 81.05) |
Limited Health System | 18.34(17.35 ~ 19.46) | | 105.85(100.07 ~ 112.33) | | 30.2(28.71~)31.72 | | 170.46(162.24 ~ 178.94) |
Minimal Health System | 2.04(1.85 ~ 2.25) | | 190.7(173.24 ~ 210.09) | | 3.07(2.74~)3.3 | | 280.32(251.02 ~ 301.7) |
Both sexes experienced a substantial rise in the number of incident cases, DALYs, and deaths, with males exhibiting significantly higher ASR for DALYs and deaths (Tables 1–3). When analyzing the data by age groups, it is observed that in 2021, all age groups reported higher incidence, DALYs, and deaths compared to 2020 (Fig. 1). Notably, the age group 5–14 years recorded the highest peak of incident cases in both years with a negative correlation between age and incident cases, except for the under-five age group (Fig. 1 and Table S1). Conversely, the age groups with the highest peaks of DALYs and deaths were consistently in the 65–74 years range in both 2020 and 2021 (Fig. 1).
The COVID-19 burden in different regions
In 2020, the regions with the highest number of incident cases were South Asia, North Africa and the Middle East, and Western Sub-Saharan Africa, with 55.934 million (95% UI 51.089 to 61.689), 19.451 million (95% UI 15.349 to 22.516), and 18.196 million (95% UI 17.060 to 19.357) cases, respectively (Fig. 2A). In contrast, Australasia reported the lowest number of incident cases at 0.0083 million (95% UI 0.0071 to 0.0095) (Fig. 2A and Table S2). In the following year, South Asia continued to report the highest number of incidence cases, followed by Eastern Sub-Saharan Africa and Southeast Asia, with 23.298 million (95% UI 21.603 to 24.777) and 21.735 million (95% UI 19.748 to 23.750) cases, respectively, while East Asia reported the lowest at 0.019 million (95% UI 0.017 to 0.025) (Fig. 2A and Table S2).
Regarding the geographic distribution of DALYs, South Asia and North Africa and the Middle East consistently had the highest numbers in both 2020 and 2021, while Australasia consistently had the lowest (Fig. 2B). Similarly, these two regions also reported the highest number of deaths over the same period, with Australasia reporting the fewest (Fig. 2C). This indicates that South Asia bore the brunt of incident cases, DALYs, and deaths, whereas Australasia was the least affected (Fig. 2).
In 2020, Central Sub-Saharan Africa had the highest ASIR for COVID-19 at 46,494.85 (95% UI 30,970.95 to 54,215.83) (Fig. 3A). Meanwhile, Andean Latin America had the highest ASR of DALYs and ASDR, with 6,719.20 (95% UI 5,787.89 to 7,811.69) and 284.67 (95% UI 246.28 to 330.39), respectively (Fig. 3B and 3C). In 2021, Eastern Europe reported the highest ASIR, and Southern Sub-Saharan Africa had the highest ASR of DALYs and ASDR (Fig. 3). Conversely, East Asia had the lowest rates of ASR for incidence, DALYs, and deaths in both years (Fig. 3 and Table S2).
The COVID-19 burden in different countries
The COVID-19 burden varied significantly among countries over the two-year period. As shown in Fig. 4A, the highest ASIR were observed in Iraq (67,238.93 [95% UI 37,127.66 to 87,270.32]), the Plurinational State of Bolivia (58,644.94 [95% UI 43,933.28 to 69,280.99]), and Armenia (52,896.41 [95% UI 31,646.71 to 65,366.89]) in 2020. In contrast, in 2021, the Northern Mariana Islands reported the highest ASIR at 138,475.1498 [95% UI 113,326.37 to 171,180.04], followed by American Samoa (93,568.16 [95% UI 88,542.16 to 95,723.18]), and Mozambique (80,599.03 [95% UI 61,759.86 to 89,911.92]) (Fig. 4B and Table S3).
The ASDR and ASR of DALYs fluctuated at the national level within these two years. The Kingdom of Eswatini had the highest ASDR and ASR of DALYs in both 2020 and 2021 (Figs. 4C-4F). However, it is noteworthy that there are a few countries with zero statistics, which might suggest that these areas have been unaffected by the COVID-19 pandemic or that there are limitations in the statistical data collection (Table S3).
The COVID-19 burden in five SDI regions
In both 2020 and 2021, the low-middle SDI regions experienced the highest incidence and DALYs, with the middle SDI regions following closely behind (Tables 1–2). Concurrently, the low SDI regions were marked by the highest ASIR and ASRs of DALYs, succeeded by the low-middle SDI regions (Tables 1–2). Regardless of whether considering incidence or ASIR, the high SDI regions consistently exhibited the lowest burden (Table 1). In 2020, the high-middle SDI regions reported the lowest number and ASR of DALYs, yet in 2021, it was the high SDI regions that demonstrated the lowest figures for both metrics (Table 2). The ASDR of COVID-19 was most pronounced in the low SDI region in 2020, at 145.97 (95% UI 138.16 to 156.68), and was least significant in the high-middle SDI region, at 37.93 (95% UI 34.91 to 41.36) (Table 3). In 2021, the low SDI region again had the highest ASDR with 242.08 (95% UI 227.27 to 256.33), while the high SDI region presented the lowest value with 45.84 (95% UI 44.39 to 47.59) (Table 3).
The COVID-19 burden in four health-system regions
Further analysis of COVID-19 epidemiology, stratified by health system, reveals a consistent upward trend in incidence across all regions. The LHS region experienced the highest number of incident cases, with 8.62 billion (95% UI 8.08 to 9.2) in 2020 and an increase to 12.13 billion (95% UI 11.84 to 14.06) in 2021 (Table 1). In contrast, the region with the MHS region had the lowest incident cases, at 1.14 billion (95% UI 0.95 to 1.26) in 2020, rising to 1.3 billion (95% UI 1.13 to 1.47) in 2021 (Table 1). Between 2020 and 2021, the MHS region consistently reported the highest ASR for incidence, DALYs, and deaths (Table 1–3). Conversely, the regions with either the AHS or the BHS consistently had the lowest ASR in these categories. This indicated that regions with better health systems tended to have a lower burden of COVID-19.
The correlation between ASR and SDI
As illustrated in Fig. 5A, there was a significant negative correlation between the ASIR of COVID-19 and SDI levels of 21 regions (R=-0.44, P < 0.001). Similarly, a negative correlation was observed between SDI levels of 21 regions and ASDR (R=-0.55, P < 0.001), as well as between SDI levels and the ASR of DALYs (R=-0.55, P < 0.001) (Fig. 5B-5C). Furthermore, we detected the correlation between ASR and SDI of 204 countries and territories, the ASIR of COVID-19 showed a negative relationship with the SDI level (R=-0.27, P < 0.001) (Fig. 6A). Similarly, the ASR of DALYs (R=-0.44, P < 0.001) and ASDR (R=-0.44, P < 0.001) also exhibited a negative correlation with the SDI (Fig. 6B-6C). Those correlations indicated that regions/countries with higher SDI tended to have lower burden of COVID-19.