Table 2 Findings on facility size

Bowblis (2020) (N = 292) Number of beds consistently showed no association with the likelihood of having at least one resident infected in COVID-19.

He (2020) (N = 1223) Larger homes with higher bed occupancy were positively associated with having one or more COVID-19 case (OR: 1.009, 95%CI 1.006–1.012) and COVID-19 mortality (OR 1.006, 95%CI 1.003–1.009). Adjusted for ownership and years of operation.

Bowblis (2020) (N = 292) Facilities with a larger number of beds were less likely to report a high number of cases at two of three time points (marginal effects for April: mean − 0.012, SE 0.010; May: mean − 0.025, SE −0.012 (p < 0.05); June; mean − 0.032, SE 0.007 (p < 0.01)). Adjusted for facility structural, occupancy and payer-mix, resident and case-mix characteristics, and rurality.

Inns (2018) (N = 379) The size of the facility was associated with the duration of the outbreak with larger care homes having longer lasting outbreaks (IRR 1.426, 95%CI 1.275–1.595,

p < 0.001). Adjusted for total outbreaks, winter outbreaks, care home quality rating, bed-to-staff ratio, residents with dementia and closure of home within 3 days.

Halloran (2020) (N = 154) No difference in the risks of an influenza outbreak between smaller homes (< 30 residents) and larger homes (> 30 residents) (p = 0.65).

Li (1996) (N = 171) A greater number of beds was associated with nosocomial respiratory and gastrointestinal disease outbreaks (RR 1.005, 95%CI 1.002–1.009). Adjusted for infection control actions such as medical protocols and laboratory results, and authorities’ area offices.

Halloran (2020) (N = 154) Compared to smaller facilities, larger facilities (≥51 residents) had a lower risk of having residents with influenza like illness once an outbreak had been declared (RR 0.55, 95%CI 0.38–0.80, p < 0.001). Adjusted for dementia care, care home quality score and antiviral prophylaxis activation.

Lin (2011) (N = 748) Higher rates of norovirus outbreaks observed in larger care homes (RR 1.4, 95%CI 1.3–1.5, p < 0.0001). Adjusted for staff-to-resident ratio, age of residents, bedridden residents, wheelchair accessibility and partition between beds.

Shallcross (2021). (N = 5126) No difference observed when comparing smaller care homes (< 25 beds) with larger care homes on the likelihood of a large outbreak (defined as 1/3 residents infected) (25–50 beds OR 0.70, 95%CI 0.41–1.19; > 50 beds OR 1.13, 95%CI 0.66–1.96). Adjusted for social deprivation, provider type, staff-to-bed ratio, region, quality rating, staff sick pay, cohorting of staff, cleaning frequency, use of personal protective equipment, inability to isolate residents, new admissions and closure to visitors.

Lomardo (2020) (N = 1356) COVID-19 outbreak associated with facility size larger than the median of 60 beds (OR 1.50, 95%CI 1.09–2.07, p = 0.013). Adjusted for lack of personal protective equipment, lack of personnel, lack of information, difficulty transferring, difficulty isolating, lack of medication, beds-to-staff ratio and geographical area.

Stall (2020) (N = 623) Larger homes with more residents were protectively associated with the number of residents infected with COVID-19 (RR 0.84, 95%CI 0.73–0.95) and resident deaths in COVID-19 (RR 0.81, 95%CI 0.70–0.95). Adjusted for chain ownership and staff-to-bed ratio.

Morciano (2021) (N = 4428) Larger homes had higher risk of COVID-19 deaths per bed: small homes (0–23 beds) OR 2.2, 95%CI 1.8–2.7; medium homes (24–40 beds) OR 4.7, 95%CI 4.0–5.5; large homes (41+ beds) OR 8.6, 95%CI 7.3–10.0. Adjusted for dementia care, legal status and provider type.

Shallcross (2021) (N = 5126) Larger care homes (> 50 beds) were significantly more likely to have a COVID-19 outbreak compared to smaller care homes defined as < 25 beds (reference). Care homes with 25–50 beds OR 1.73, 95%CI 1.30–2.31; > 50 beds OR 2.76, 95%CI 1.97–3.88). Adjusted for social deprivation, provider type, staff-to-bed ratio, region, quality rating, staff sick pay, cohorting of staff, cleaning frequency, use of personal protective equipment, inability to isolate residents, new admissions and closure to visitors.

Stall (2020) (N = 623) Homes with larger numbers of residents were significantly associated with greater odds of an outbreak (OR 1.38, 95%CI 1.18–1.61). Adjusted for chain ownership and staff-to-bed ratio.

White (2020) (N = 3357) Larger facility (presented as a 10-bed difference in facility size) was associated with greater probability of having at least one resident with COVID-19 infection. Marginal effect: 0.90, SE 0.159, p < 0.001. Findings adjusted for county COVID-19 prevalence, date of first county case, and universal testing at facility.