key: cord-0963199-0xhlt9wm
authors: Domingo, Pere; Pomar, Virgina; Mur, Isabel; Castellví, Ivan; Corominas, Héctor; de Benito, Natividad
title: Not all COVID-19 pandemic waves are alike
date: 2021-04-19
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2021.04.005
sha: 76063342ae42681a488ee5bd9f28ca5008255034
doc_id: 963199
cord_uid: 0xhlt9wm

OBJECTIVE: We aimed to assess differences in patients’ profiles in the first two surges of the SARS-CoV-2 pandemic in Barcelona, Spain. METHODS: We prospectively collected data from all adult patients with SARS-CoV-2 infection diagnosed at the Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. All the patients were diagnosed through nasopharyngeal swab PCR. The first surge spanned from March 1 to August 13, 2020, while surge two encompasses August 14 to December 8, 2020. RESULTS: There were 2479 and 852 patients with microbiologically proved SARS-CoV-2 infection in surge one and two, respectively. Patients from surge two were significantly younger (median age: 52 [IQR: 35] vs. 59 [40] years, respectively, P < 0.001), had fewer comorbidities (379/852, 44.5% vs. 1237/2479, 49.9%, P = 0.007), and a shorter interval between onset of symptoms-diagnosis (median: 3 [5] vs. 4 [5] days, P < 0.001). All-cause in-hospital mortality significantly decreased both for the whole population (24/852, 2.8% vs. 218/2479, 8.8%, P < 0.001) and hospitalized patients (20/302, 6.6% vs. 206/1570, 13.1%, P = 0.012). At adjusted logistic regression analysis, predictors of in-hospital mortality were older age (per year, adjusted odds ratio [aOR] 1.079, 95% CI: 1.063-1.094), male sex (aOR 1.476, 95% CI: 1.079-2.018), having comorbidities (aOR 1.414, 95% CI: 0.934-2.141), ICU admission (aOR 3.812, 95% CI: 1.875-7.751), mechanical ventilation (aOR 2.076, 95% CI: 0.968-4.454), and COVID-19 during surge one (with respect to surge two) (aOR 2.176, CI: 95% 1.286-3.680). CONCLUSIONS: First wave SARS-CoV-2-infected patients had a more than two-fold higher in-hospital mortality than second-wave patients. The causes are likely multifactorial.

Objective: We aimed to assess differences in patients' profiles in the first two surges 34 of the SARS-CoV-2 pandemic in Barcelona 

However, this ratio reversed when patients admitted to the hospital were considered (Table   108 2). In surge two, a microbiological diagnosis was obtained fewer days after the onset of 109 symptoms, and infiltrates in chest X-ray were less common (Table 1) . Significantly more 110 patients from the first wave were admitted to the hospital, although the length of hospital 111 stay was not significantly different (Tables 1 and 2) .

Regarding all SARS-CoV-2-diagnosed patients, those admitted to the hospital were older, 113 although hospitalized in surge two were still younger than patients hospitalized in surge one 114 ( Table 2) . We found that inpatients in surge two had more comorbidities and required more 115 often Intensive Care Unit (ICU) admission and mechanical ventilation; despite that, the all-116 cause mortality was substantially lower, particularly in patients older than 65 years. After 117 adjusting for relevant clinical variables (Table 3) , first-wave patients had a more than two-fold 118 higher all-cause in-hospital mortality than second-wave patients. Table 2 ). The preferred immunomodulating 135 agent in our hospital was tocilizumab, and combination therapy was not often used.

We cannot thoroughly exclude viral changes implying shifts in SARS-CoV-2 pathogenicity. (Table   155 1). Besides, the enormous efforts made to protect this vulnerable population may have 156 impacted its reduced representation during the second wave.

The decreased hospital admission rates and pulmonary infiltrates during the second 158 pandemic wave suggest milder disease (Table 1) 

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