In this retrospective study, we compared the prevalence of hospital acquired respiratory infections in pre- and during COVID-19 period. With strict prevention and control measures, such as reduce unnecessary visits, reduce and fixed caregivers, increase the ward bed space (at least 1 meter), supervise the implantation of hand hygiene and wearing N95 masks etc., the incidence of nosocomial respiratory infections are greatly decreased from 4.2–2.9%, p = 0.001.
In our study, the incidence of hospital acquired respiratory infections was similar to reports from other countries, which was ranging from 1–4.7%. The annual incidence rate of HAIs in a teaching hospital in the south of Iran was 1.46% [8, 9].A study to quantify the incidence and influence of NV-HAP in the United States using a national dataset showed that the incidence of NV-HAP was 1.6%[9].A randomized, parallel-group, controlled trial about elder patients in a tertiary hospital geriatric unit in US showed the incidence of nosocomial pneumonia was4.7%[10]. A 3-year surveillance study on the epidemiological and clinical characteristics of healthcare associated-infections (HAIs) in elderly inpatients in a large tertiary hospital in China showed the incidence of the lower respiratory tract infection was 0.85% [11]. It was lower than a multicenter study in China which incidence of HAP was 7.72%.[12] This may be due to the strict diagnostic criteria in our study[7]. Besides, in our study patients were mainly from non-ICU department, and included both elder and non-elder patients.
Many studies have been conducted on prevention of HAIs. Respiratory tract is one of the most common infection sites, can cause elevated morbidity, mortality and increased hospital costs. Experiences have shown that hospital acquired infections decreased after adopting prevention measures. But hospital acquired pneumonia was in a stable prevalence [5]. Similarly, an analysis of Medicare Patient Safety Monitoring System data showed that, between 2005 and 2013, the percentage of patients with ventilator-associated pneumonia among eligible Medicare patients with selected diagnoses who were undergoing mechanical ventilation remained the same, at approximately 10%.[13] A randomized, parallel-group, controlled trial was undertaken in patients aged 65 and above who were admitted to a tertiary hospital geriatric. 59 patients treated with multi-component intervention (consisting of reverse Trendelenburg position, dysphagia screening, oral care and vaccinations) had similar incidence of nosocomial pneumonia with patients of usual care (64 patients). However, this study had only 4 hospital acquired pneumonia patients, making the study under-powered.[10]
Despite poor outcome caused by hospital acquired respiratory infection [9, 14], few studies paid special attention to non-ventilator-associated pneumonia in hospitalized patients. Some investigators have called for increased attention and resources for this underappreciated health care associated infection.[15–17] The majority of pneumonia events in hospitals in our survey were not ventilator-associated.
The main prevention measures mentioned in literature including hand hygiene, decolonization, decreased aspiration risk, droplet isolation, protective isolation and contact precautions.[18]
A Chinese longitudinal study from 2017 to 2020 in a provincial general teaching hospital showed that improvement in HH compliance was associated with a decline in the incidence of HAIs. In this study the compliance of hand hygiene increased form 68.9–91.76%, and the incidence of HAIs decreased from 1.1–0.91%, p < 0.01[19]. A historical control study in China showed the adherence of hand hygiene and mask-wearing during the COVID-19 pandemic (from February 1 to June 29, 2020) increased from 66–92%. The mean incidence of HAP decreased from 0.0538 to 0.0204 per month per patient [20].
An intervention review conducted in 2018 aimed to assess effects of oral care measures for preventing nursing home-acquired pneumonia in residents of nursing homes and other long-term care facilities. No conclusive evidence showed oral care reduces the incidence of pneumonia [21]. Other meta-analysis studies showed oral care interventions was associated with a significant risk reduction for developing pneumonia in non-ventilated patients [22, 23]. However, selection bias in those primary RCTs made us interpreted the overall effect with caution.
During COVID-19 period, all patients without contraindications of wearing masks, healthcare staffs, and caregivers were asked to wear masks in our hospital. (Healthcare staffs use N95 masks. Patients and their caregivers use surgical masks.) The compliance of wearing masks was monitored by the hospital Infection control department. A few studies in regards to the effectiveness of face mask indicated significant effect against respiratory infections [24]. Researches about the effectiveness of face masks in preventing influenza showed less contacts became symptomatic in the mask group compared to the control group (31% versus 53%, p = 0.04)[24].But the endpoints varied in these studies, from acute respiratory infections to any one of respiratory symptoms.
But there are limited studies concerning expanded bed space, reduced visiting and fixed caregivers for patients on hospital associated infection. A simulation study showed that social distancing and PPE use significantly reduced the transmission rate of SARS-CoV-2 within the laboratory environment. The strongest protective effect is seen with the N95 masks [25]. A population-based retrospective cohort study of risks of HAP in adult patients over 3 years showed that the risk of HAP was approximately three times higher in patients who stayed in rooms with more than four beds than that in those who stayed in rooms with three or fewer beds[26]. Similarly, a meta-analysis represent that compared to those who stay in multiple-patient rooms, using a single-patient room can reduce the hospital associated colonization of MDR pathogens and bacteremia rate[27]. Limited studies concerned association of caregivers with hospital associated infection. Patients who stayed in a ward with a caregiver had 1.19-fold higher risk of HAP than those who were cared for only by nurses. The researchers suggested educating caregivers and patients about hand hygiene and other preventive behaviors to reduce the risk of HAP [26]. During COVID-19 period, every ward in our hospital was requested to expend distance between beds, so that the 3 patients-room turned to 2 patients-rooms. For patients who need a caregiver, each patient had one caregiver, all of the caregivers were educated about hand hygiene and asked to wear facial mask. Except for education and monitoring of prevention and control measures, people’s fear of COVID-19 led to high compliance of prevention and control measures. This greatly reduced the risk of hospital acquired respiratory tract infection. In our study, the incidence of hospital acquired respiratory tract infection decreased form 4.2–2.9% compared to pre-COVID-19 period.
The all-cause mortality rate of hospital acquired respiratory tract infection patients was 34.03%, was much higher than these reported in previous studies, which varied from 13–22.6%. A 10-year prospective observational study in 15 Chinese teaching hospitals showed that the all-cause mortality of HAP was 13.7% [28]. In another HAP clinical survey in 13 large teaching hospitals, the all-cause mortality was 22.3%[29].A prospective study carried out in 25 hospitals in China from November 2015 to June 2016 showed the 3 months mortality among bedridden patients with HAP was 16.56%[30].VAP was considered a subgroup of HAP in these studies, which mortality was considered higher than NV-HAP[9]. However, studies focused on NV-HAP showed that in hospital mortality rate of NV-HAP varied from 13%-30% [9, 31–33].
Active immunosuppressant therapy, solid tumor, coma, clinical pulmonary infection score(CPIS) ≧ 7, infection occurred in ICU, age ≧ 65 years, tracheal cannula insertion, and number of comorbidities were considered to be independent risk factors for mortality[28–30]. In our study, patients’ median age was 85 years, while in these studies mentioned above, the median age was about 65 years or below. More elder patients in our study might be an important reason for high mortality rate. However, we didn’t analyze the mortality rate of non-hospital acquired respiratory tract infection. The multivariate logistic regression of our study identified 2 independent factors associated with in-hospital mortality: severe pneumonia (OR 28.235, 95% CI 10.122–78.759), and previous malignant tumor (OR 4.599, 95%CI 1.768–11.963). Patients with cardiac injury may had higher mortality (OR 2.264, 95%CI 0.935–5.485), but there was no significant difference, p = 0.07. As mentioned before, patients with hospital acquired respiratory tract infection in our study mostly were elders. Elder patients were more likely combined with comorbidities, severe respiratory tract infections, less likely admitted to ICU (Patients and their families were more likely not to be admitted to the ICU.).