ABSTRACT
Following the announcement of coronavirus disease 2019 (COVID-19) cases in Wuhan on 31 December 2019, government officials in Hong Kong recommended the wearing of face masks as a public infection control measure against the COVID-19 virus and curtail the impact of the concurrent influenza season. The present study evaluated the influenza-related outcomes between the influenza season 2019 and 2020 in Hong Kong as a result of these infection control measures. A Monte Carlo simulation model was designed to estimate the number of influenza cases, clinic visits, hospitalization, deaths, direct medical cost and disability-adjusted life-years (DALYs) for the season 2018–2019 and 2019–2020 in six age groups: 0–5 years, 6–11 years, 12–17 years, 18–49 years, 50–64 years and ≥65 years in Hong Kong. Model inputs were derived from public data and existing literature. The model findings showed significant reduction in influenza-related cases, clinic visits, hospitalization, and deaths in 2020 versus 2019 (p < 0.05). Influenza-related direct costs in all age-groups were significantly reduced by 56%-82% (p < 0.01) in 2020 versus 2019. DALYs were also significantly decreased by 58%-85% (p < 0.01). The direct cost and DALYs avoided in 2020 was the highest among the age group of 0–5 years with a cost-saving of USD593,763 (95%CI 590,730–596,796) per 10,000 population and a DALY reduction of 57.67 (95%CI 57.54–57.83) per 10,000 population. This study illustrated the reduction of all influenza-related outcome measures in Hong Kong as a result of the implementation of public infection control measures against COVID-19.
KEYWORDS: Seasonal influenza, COVID-19, face mask, health economics, disability-adjusted life-years
Introduction
The coronavirus disease 2019 (COVID-19) pandemic has imposed a catastrophic impact around the world. Reports of the first cluster of an unusual strain of pneumonia cases were made by Wuhan Municipal Health Commission, China, on 31 December 2019 [1]. Immediately following this announcement, the Government of Hong Kong Special Administrative Region issued recommendations on public infection control measures. These included good personal and environmental hygiene, promotion of influenza vaccination as well as the use of face masks [2]. As a result of these recommendation, influenza vaccine recipients in Hong Kong increased by 17.4% in 2020 when compared to the previous year [3]. An epidemiology study further validated the public’s acceptance of these recommendations with a reported high daily compliance of mask-wearing (>95%) observed in all districts of Hong Kong [3,4].
Each year, the public healthcare provider of Hong Kong is consistently burdened by the surge of influenza-like illnesses during the peak of influenza season. Public hospitals are often crowded to maximum capacity due to severe influenza admissions [5]. However, in the 2019–2020 influenza season, influenza admissions were reportedly reduced and the influenza season ended by February 2020 (versus May 2016 for 2015–2016 and April 2019 for 2018–2019) [6–8]. The impact of these changes on healthcare outcomes before and amid the COVID-19 pandemic are yet to be investigated. This study aimed to evaluate the age-specific influenza-related outcomes in 2019 and 2020 from the perspective of the public healthcare provider in Hong Kong.
Materials and methods
Model design
A Monte Carlo simulation model was designed, using the TreeAge Pro Healthcare 2020 (TreeAge Software, Inc., Williamstown, MA, USA) and Microsoft Excel 2016 (Microsoft Corporation, Redmond, WA, USA), to estimate the influenza-related cases, clinic visits, hospitalizations, deaths, cost, and DALYs in the weeks of 1–26 of 2019 and 2020 for six age groups in the Hong Kong population: 0–5 years, 6–11 years, 12–17 years, 18–49 years, 50–64 years, and ≥65 years.
The present study adopted the Centers for Disease Control and Prevention’s well-described methods of estimating influenza cases [9–11]. Briefly, influenza-associated hospitalization admission rates reported by the Department of Health was first corrected by under-detection multipliers. The adjusted rate of hospitalization was further extrapolated to the population for estimation of (1) influenza cases (by case-to-hospitalization ratio) and (2) influenza-associated deaths (by death-to-hospitalization ratio). The number of medical visits for influenza was approximated from the estimated number of influenza cases (by proportion of medical visit among cases). Monte Carlo simulations were conducted to simulate 10,000 trials for each age group in influenza season 2019 and 2020 by randomly drawing the model inputs from the range of uncertainty.
Model inputs
All model inputs were shown in Tables 1–4. Age-group specific influenza-associated admission rates (per 10,000 population of the age group) in public hospitals were retrieved for 26 weeks (week 1–26) in 2019 and 2020 from the weekly report produced by the Respiratory Disease Office of the Center for Health Protection, Department of Health in Hong Kong [12], while age-specific distribution of Hong Kong populations in 2019 were obtained from the Census and Statistics Department of Hong Kong [13]. Parameters used for estimation of influenza cases, deaths, and clinic visits from reported hospital admission rate were retrieved from outcomes studies of influenza in the US [9–11,14].
Table 1.
Monte Carlo Simulation model inputs
| Base-case value | Range of uncertainty | Reference | |
|---|---|---|---|
| Case-to-hospitalization ratio | |||
| Age 0–5 years | 143.4 | 129–158 | [11] |
| Age 6–11 years | 364.7 | 328–401 | |
| Age 12–17 years | 364.7 | 328–401 | |
| Age 18–49 years | 178.2 | 160–196 | |
| Age 50–64 years | 94.3 | 85–104 | |
| Age ≥65 years | 11.0 | 10–12 | |
| Death-to-hospitalization ratioa | [9,10] | ||
| Age 0–5 years | 0.0105 | 0.0095–0.0116 | |
| Age 6–11 years | 0.0100 | 0.0090–0.0110 | |
| Age 12–17 years | 0.0100 | 0.0090–0.0110 | |
| Age 18–49 years | 0.0366 | 0.0329–0.0403 | |
| Age 50–64 years | 0.0579 | 0.0521–0.0637 | |
| Age ≥65 years | 0.0915 | 0.0829–0.1007 | |
| Proportion of medical visit among cases | [14] | ||
| Age 0–5 years | 0.67 | 0.60–0.74 | |
| Age 6–11 years | 0.52 | 0.47–0.57 | |
| Age 12–17 years | 0.52 | 0.47–0.57 | |
| Age 18–49 years | 0.37 | 0.33–0.41 | |
| Age 50–64 years | 0.43 | 0.39–0.47 | |
| Age ≥65 years | 0.56 | 0.50–0.62 | |
| Under-detection multiplier on hospitalizationb | 1 | - | |
| Age-specific utility | [15] | ||
| <18 years | 1.0 | - | |
| 18–64 years | 0.92 | - | |
| ≥65 years | 0.84 | - | |
| Disutility of influenza | [16–18] | ||
| Self-care | 0.2 | 0.16–0.24 | |
| Outpatient medical care | 0.4 | 0.23–0.45 | |
| Hospitalization | 0.5 | 0.4–0.6 | |
| Length of illness (day) | [18,19] | ||
| Self-care | 5 | 4–7 | |
| Outpatient medical care | 5 | 4–7 | |
| Hospitalization stay | [18,19] | ||
| Age <18 years | 3 | 1–13 | |
| Age ≥18 years | 6 | 3–20 | |
| Number clinic visit per case | 1 | 1–2 | |
| Cost (HKD) | [21] | ||
| Clinic visit | 57 | - | |
| Accident and Emergency visit | 158 | - | |
| Hospitalization per day | 654 | - |
a: No influenza-related death was reported in age groups <18 years in week 1–26 of 2020, the death:hospitalization ratios of age<18 years therefore adopted a value of 0 in 2020.
b: The weekly reporting system of influenza-associated hospital admission has been well established in Hong Kong, the under-detection multiplier therefore adopted a value of 1.
Table 2.
Influenza-associated hospital admission rates reported in Hong Kong 2019
| |
Number per 10,000 in the age group [12]a |
|
|||||
|---|---|---|---|---|---|---|---|
| Week | 0–5y | 6–11y | 12–17y | 18–49y | 50–64y | ≥65y | |
| 1 | 6.04 | 1.1 | 0.25 | 0.25 | 0.44 | 1.2 | |
| 2 | 9.23 | 1.84 | 0.59 | 0.36 | 0.74 | 1.89 | |
| 3 | 10.58 | 1.9 | 1.2 | 0.52 | 0.8 | 1.93 | |
| 4 | 7.65 | 1.62 | 0.46 | 0.37 | 0.61 | 2.29 | |
| 5 | 4.36 | 1.05 | 0.4 | 0.29 | 0.52 | 1.46 | |
| 6 | 3.5 | 0.72 | 0.18 | 0.15 | 0.41 | 1.12 | |
| 7 | 4.12 | 0.85 | 0.15 | 0.23 | 0.34 | 1.07 | |
| 8 | 3.38 | 0.83 | 0.25 | 0.21 | 0.3 | 1.22 | |
| 9 | 3.83 | 0.94 | 0.25 | 0.13 | 0.23 | 0.96 | |
| 10 | 2.69 | 0.94 | 0.15 | 0.18 | 0.21 | 0.8 | |
| 11 | 2.81 | 0.83 | 0.4 | 0.13 | 0.22 | 0.87 | |
| 12 | 1.7 | 0.66 | 0.52 | 0.1 | 0.19 | 0.88 | |
| 13 | 1.52 | 0.55 | 0.15 | 0.1 | 0.17 | 0.82 | |
| 14 | 1.08 | 0.63 | 0.15 | 0.1 | 0.11 | 0.38 | |
| 15 | 1.11 | 0.36 | 0.03 | 0.06 | 0.09 | 0.3 | |
| 16 | 1.2 | 0.63 | 0.03 | 0.09 | 0.05 | 0.23 | |
| 17 | 1.61 | 0.82 | 0.18 | 0.13 | 0.11 | 0.36 | |
| 18 | 1.46 | 0.3 | 0.21 | 0.09 | 0.05 | 0.17 | |
| 19 | 0.87 | 0.49 | 0.12 | 0.04 | 0.03 | 0.18 | |
| 20 | 0.87 | 0.9 | 0.37 | 0.06 | 0.04 | 0.14 | |
| 21 | 1.4 | 0.87 | 0.49 | 0.08 | 0.03 | 0.18 | |
| 22 | 0.75 | 0.76 | 0.24 | 0.06 | 0.04 | 0.18 | |
| 23 | 0.84 | 0.93 | 0.46 | 0.05 | 0.07 | 0.2 | |
| 24 | 1.28 | 0.82 | 0.15 | 0.07 | 0.06 | 0.3 | |
| 25 | 1.43 | 1.23 | 0.24 | 0.08 | 0.07 | 0.25 | |
| 26 | 1.52 | 0.87 | 0.31 | 0.11 | 0.08 | 0.17 | |
a: Range of uncertainty for Monte Carlo simulation: ±10% of reported admission rate
Table 3.
Influenza-associated hospital admission rates reported in Hong Kong 2020
| |
Number per 10,000 in the age group [12]a |
|
|
|||
|---|---|---|---|---|---|---|
| Week | 0–5y | 6–11y | 12–17y | 18–49y | 50–64y | ≥65y |
| 1 | 2.66 | 0.59 | 0.56 | 0.15 | 0.22 | 0.64 |
| 2 | 4.45 | 1.08 | 0.59 | 0.26 | 0.37 | 1.25 |
| 3 | 3.31 | 0.86 | 0.31 | 0.28 | 0.47 | 1.47 |
| 4 | 3.31 | 0.86 | 0.43 | 0.41 | 0.5 | 1.28 |
| 5 | 1.52 | 0.48 | 0.31 | 0.32 | 0.4 | 1.03 |
| 6 | 0.63 | 0.16 | 0.09 | 0.12 | 0.16 | 0.44 |
| 7 | 0.06 | 0.03 | 0.03 | 0.03 | 0.03 | 0.14 |
| 8 | 0 | 0 | 0.03 | 0.01 | 0.01 | 0.01 |
| 9 | 0 | 0 | 0 | 0.01 | 0.02 | 0.04 |
| 10 | 0.03 | 0 | 0 | 0.003 | 0 | 0.01 |
| 11 | 0.03 | 0.05 | 0.03 | 0.02 | 0 | 0.01 |
| 12 | 0.06 | 0.03 | 0.06 | 0.04 | 0 | 0.01 |
| 13 | 0.03 | 0 | 0.03 | 0.01 | 0.01 | 0.02 |
| 14 | 0.03 | 0.03 | 0 | 0.003 | 0 | 0 |
| 15 | 0 | 0 | 0.03 | 0 | 0 | 0 |
| 16 | 0 | 0 | 0 | 0 | 0 | 0 |
| 17 | 0 | 0 | 0 | 0.003 | 0 | 0.01 |
| 18 | 0 | 0 | 0 | 0 | 0 | 0 |
| 19 | 0 | 0 | 0 | 0 | 0 | 0 |
| 20 | 0 | 0 | 0 | 0 | 0 | 0 |
| 21 | 0 | 0 | 0 | 0.003 | 0 | 0 |
| 22 | 0 | 0 | 0 | 0 | 0 | 0 |
| 23 | 0 | 0 | 0 | 0 | 0 | 0.01 |
| 24 | 0 | 0 | 0 | 0 | 0 | 0 |
| 25 | 0 | 0 | 0 | 0 | 0.01 | 0 |
| 26 | 0 | 0 | 0 | 0 | 0 | 0 |
a: Range of uncertainty for Monte Carlo simulation: ±10% of reported admission rate
Table 4.
Hong Kong population (N = 7,500,700) distribution by age in 2019
| Age-specific groups [13] | % |
|---|---|
| 0–5 years | 3.6% |
| 6–11 years | 4.1% |
| 12–17 years | 7.7% |
| 18–49 years | 42.8% |
| 50–64 years | 23.9% |
| ≥65 years | 18.0% |
The DALYs associated with influenza infection were estimated using the age-specific utility score, disutility of the event, and the duration of time-spent in each of following events: (1) self-treated influenza; (2) outpatient care; and (3) hospitalization. The utility value of each health status was estimated from findings of health-related quality of life studies [15–18]. The time-spent in outpatient care and hospitalization were inferred from the duration of illness and length of hospital stay, correspondingly [18,19]. The DALY of influenza-related death was calculated using age-specific expectation of life reported in the Hong Kong life table 2019 and age-specific utility value, discounted by an annual rate of 3% [15,20].
Analysis of direct medical cost was conducted from the perspective of the Hospital Authority, the largest nonprofit-making public healthcare provider of Hong Kong. Cost items of influenza treatment included outpatient care and hospitalization. The number of clinic visits for outpatient care was assumed to be one (range 1–2 visits). The cost per general outpatient clinic visit, and cost per hospital day were estimated from the 2020 charges of Hospital Authority. The charges listed represent the cost components (including manpower costs) with no addition of profits [21].
Results
The predictive validity of model outputs was examined by comparing the expected deaths (estimated by the present model) in year 2019 and year 2020 with the number of deaths reported by the Center for Health and Protection in Hong Kong. The total numbers of deaths predicted by the model were 378 and 121 in week 1–26 of 2019 and 2020, respectively. The predicted values were similar to the reported findings (356 deaths in 2019; 113 deaths in 2020) [7,8] with relative difference of 6–7%.
Table 5 shows the age group-specific influenza-related outcomes (cases, clinic visits, hospitalization, and death per 10,000 population), and cost and DALYs are shown in Table 6. All influenza-related outcome measures were significantly reduced in 2020 versus 2019 (p < 0.05). Influenza-related direct costs in all age-groups were significantly reduced by 56%-82% (p < 0.01) in 2020 when comparing to year 2019 and the DALYs also significantly decreased in 2020 by 58%-85% (p < 0.01). The direct cost and DALYs avoided in 2020 were the highest in the age group 0–5 years with a cost saving of USD593,763 (95%CI 590,730–596,796) per 10,000 population and a DALY reduction of 57.67 (95%CI 57.54–57.83) DALYs per 10,000 population.
Table 5.
Monte Carlo simulations on age-specific influenza-related cases, clinic visits, hospitalizations, and deaths in 2019 and 2020a.
| |
Per 10,000 population of each age group (95% CI) |
|||
|---|---|---|---|---|
| Cases | Clinic visits | Hospitalizations | Deaths | |
| Age 0–5 (yr) | ||||
| 2019 | 9,987 (9,986–9,989) | 6,691 (6,685–6,696) | 69.75 (69.70–69.81) | 0.7349 (0.7341–0.7357) |
| 2020 | 2,311 (2,308–2,313) | 1,546 (1,544–1,548) | 16.10 (16.09–16.12) | 0 |
| Age 6–11 (yr) | ||||
| 2019 | 8,549 (8,540–8,559) | 4,447 (4,441–4,453) | 23.45 (23.43–23.47) | 0.2421 (0.2417–0.2424) |
| 2020 | 1,528 (1,526–1,529) | 795 (794–796) | 4.190 (4.186–4.193) | 0 |
| Age 12–17 (yr) | ||||
| 2019 | 2,885 (2,881–2,888) | 1,500 (1,498–1,502) | 7.91 (7.90–7.91) | 0.0790 (0.0789–0.0791) |
| 2020 | 924 (923–925) | 480.6 (479.9–481.2) | 2.54 (2.53–2.54) | 0 |
| Age 18–49 (yr) | ||||
| 2019 | 715 (714–716) | 264 (264–265) | 4.01 (4.01–4.02) | 0.1469 (0.1467–0.1471) |
| 2020 | 295.1 (294.8–295.5) | 109.3 (109.1–109.4) | 1.658 (1.657–1.659) | 0.0607 (0.0606–0.0608) |
| Age 50–64 (yr) | ||||
| 2019 | 567 (566–568) | 244 (243–244) | 6.00 (6.00–6.01) | 0.3477 (0.3473–0.3481) |
| 2020 | 207.8 (207.6–208.0) | 89.3 (89.2–89.5) | 2.199 (2.198–2.201) | 0.1274 (0.1273–0.1276) |
| Age ≥65 (yr) | ||||
| 2019 | 215.0 (214.8–215.2) | 120 (120–121) | 19.55 (19.53–19.57) | 1.7877 (1.7856–1.7897) |
| 2020 | 69.9 (69.9–70.0) | 39.1 (39.1–39.2) | 6.36 (6.35–6.36) | 0.5818 (0.5812–0.5825) |
a: Weeks 1–26 of 2019 and 2020; difference in influenza-related events (per 10,000 population) between 2019 and 2020 achieved statistical significance (p < 0.05)
Table 6.
Monte Carlo simulations of age-specific direct medical cost and DALYs per 10,000 population in 2019 and 2020a.
| |
Mean (95% CI) |
|||
|---|---|---|---|---|
| 2019 | 2020 | Reductionb | % Reductionc | |
| Age 0–5 years | ||||
| Cost (USD) | 772,628 (769,681–775,576) | 178,865 (178,160–179,570) | 593,763 (590,730–596,796) | 75.95% (75.81%-76.08%) |
| DALYs | 68.10 (67.96–68.24) | 10.41 (10.38–10.44) | 57.67 (57.54–57.83) | 84.54% (84.48%-84.60%) |
| Age 6–11 years | ||||
| Cost (USD) | 426,810 (425,321–428,298) | 76,214 (75,947–76,480) | 350,596 (349,085–352,108) | 81.58% (81.49%-81.67%) |
| DALYs | 42.81 (42.70–42.92) | 6.34 (6.32–6.36) | 36.47 (36.35–36.58) | 84.91% (84.85%-84.98%) |
| Age 12–17 years | ||||
| Cost (USD) | 144,110 (143,600–144,619) | 46,139 (45,974–46,301) | 97,972 (97,435–98,509) | 66.93% (66.76%-67.10%) |
| DALYs | 14.35 (14.32–14.39) | 3.82 (3.81–3.84) | 10.53 (10.49–10.57) | 72.87% (72.76%-72.98%) |
| Age 18–49 years | ||||
| Cost (USD) | 45,758 (45,552–45,965) | 18,909 (18,823–18,995) | 26,850 (26,625–27,074) | 56.40% (56.11%-56.69%) |
| DALYs | 6.37 (6.36–6.38) | 2.63 (2.62–2.63) | 3.74 (3.73–3.76) | 58.43% (58.32%-58.53%) |
| Age 50–64 years | ||||
| Cost (USD) | 57,065 (56,770–57,359) | 20,831 (20,724–20,938) | 36,234 (35,920–36,547) | 60.87% (60.58%-61.16%) |
| DALYs | 8.59 (8.58–8.61) | 3.15 (3.14–3.15) | 5.44 (5.43–5.46) | 63.04% (62.95%-63.14%) |
| Age ≥65 years | ||||
| Cost (USD) | 134,301 (133,366–135,235) | 43,557 (43,248–43,865) | 90,744 (89,757–91,731) | 63.02% (62.63%-63.41%) |
| DALYs | 15.02 (15.07–15.32) | 4.94 (4.90–4.99) | 10.25 (10.12–10.39) | 59.72% (59.18%-60.26%) |
a: Week 1–26 of 2019 and 2020
b: Reduction in 2020 versus 2019; all reduction in cost and DALYs achieved statistical significance (p < 0.01)
c: % reduction in 2020 versus 2019
USD: USD1 = HKD7.8
DALY: Disability-adjusted life-years
Discussion
The present study examined the influenza-related healthcare outcomes in 2019 and 2020. The findings showed significant reduction in influenza-related outcomes for all age groups in 2020, as the winter influenza season was shortened, ending in February 2020 (compared to April 2019 in the previous season).
The increase in influenza vaccine uptake for 2019/2020 season was potentially a major factor contributing to the reduced burden of influenza in Hong Kong. The statistics on vaccination programs of Hong Kong found a 38%, 26%, 24%, and 10% relative increase in influenza vaccine uptake among children aged 6 months to <6 years, children aged 6 to <12 years, adults aged 50–64 years, and elderly aged ≥65 years, respectively [13]. This was coupled with the 2019/2020 season’s vaccine effectiveness. The interim vaccine effectiveness of the 2019/2020 influenza vaccine was reported to be 45% (95%CI 36%-53%), higher than the vaccine effectiveness of 29% (95%CI 21%-35%) for 2018/2019 [22,23].
Upon the first official reports of a cluster of pneumonia cases in Wuhan in late December of 2019, the public health officials in Hong Kong issued recommendations to the general public promoting the use of face masks and maintaining good personal/environment hygiene. Shortly thereafter, an epidemiology study of Hong Kong reported the observational findings on face mask wearing behaviors in over 10,000 persons in the community during early 2020. A high daily adherence of mask-wearing was observed (>95%) in all districts of Hong Kong. The epidemiology findings strongly suggested the positive role of community-wide face mask use in reducing the spread of COVID-19-infected respiratory droplets or saliva. As influenza is transmitted person-to-person by infected respiratory droplets or saliva, the infection control measures against COVID-19 are also effective measures to prevent the transmission of influenza as well. The willingness and compliance of the general public to wear face masks starting from pre-COVID-19 pandemic in early 2020 are therefore likely to contribute to the reduced burden of influenza in Hong Kong and subsequently a reduction in the influenza-related costs and DALYs.
During the winter influenza season of 2019, influenza outbreaks occurred in 208 kindergartens and childcare centers, and resulting in the temporary shut-down among 20% of such facilities in January 2019 [24]. Compared to the 2019 influenza season, early termination of the 2020 winter influenza season resulted in a profound reduction in the influenza burden among the younger age groups. The impact of a shortened influenza season on the reduction of healthcare costs and DALYs were substantial. These reductions were most prominent in younger age groups (age <18 years) with >66%-82% and >72%-84% reduction in direct medical cost and DALYs, respectively. Among age groups of 18 years and above, the cost and DALYs avoidance were also shown to be >55%-63%.
The present study was limited by approximating the outcomes of influenza in Hong Kong with US parameters on influenza burden estimation. The predictive validity of the model on influenza burden estimation was therefore examined by comparing the predicted deaths with reported number of mortality. In week 1–26 of 2020, there were 8 deaths from COVID-19 reported in Hong Kong [25]. The reduced burden of influenza-related deaths (113 deaths in 2020 and 356 deaths in 2019) and reduced DALYs were therefore unlikely caused by excessive deaths from COVID-19. The model included three tiers of influenza treatment (self-care, outpatients, and hospitalization) and simplified the complexity of influenza management. Model outputs might therefore underestimate the cost and DALYs of cases with severe influenza infection. Prior to COVID-19, the influenza winter season consistently ended in April-May during 2012–2019 [12]. The present study therefore only considered the most recent influenza season (2019) prior to outbreak of COVID-19 in 2020. The lack of inclusion of other prior seasons may have limited the representation of influenza outcomes during the pre-COVID-19 years.
Conclusions
Influenza-related healthcare costs and DALYs for the influenza season 2020 were significantly lowered when comparing to those of season 2019. It apparently correlated with the Hong Kong people’s willingness to follow the government officials’ recommendations on public infection control measures against COVID-19, as indicated by the increased influenza vaccination coverage and high adherence to universal masking. The high-level willingness to comply with public health recommendations in Hong Kong was a learned practice linked to the 2003 outbreak of severe acute respiratory syndrome [26]. It is reasonable to believe that such high level of willingness and adherence to vaccination and non-pharmaceutical interventions may wean off when the COVID-19 pandemic subsides. Community-wide programs are therefore essential to sustain the influenza vaccination coverage and adherence to public infection control measures during the influenza season. Future research on the cost-effective implementation of community-wide infection control programs for non-pharmaceutical measures and influenza vaccination against seasonal influenza is highly warranted.
Acknowledgments
The author wishes to thank Dr. Celeste Ewig (School of Pharmacy, The Chinese University of Hong Kong) for proofreading the manuscript.
Disclosure statement
No potential conflict of interest was reported by the author.
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