Main differences between the first and second waves of COVID-19 in Madrid, Spain

Abstract

Background: The emergence and rapid global spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) represents a major challenge to health services, and has disrupted social and economic activities worldwide. In Spain, the first pandemic wave started in mid-March 2020 and lasted for 3 months, requiring home confinement and strict lockdown. Following relaxation of the measures during the summer, a second wave commenced in mid-September 2020 and extended until Christmas 2020. Methods: The two pandemic waves were compared using information collected from rapid diagnostic tests and polymerase chain reaction assays at one university clinic in Madrid, the epicentre of the pandemic in Spain. Results: In total, 1569 individuals (968 during the first wave and 601 during the second wave) were tested for SARS-CoV-2-specific antibodies using fingerprick capillary blood. In addition, during the second wave, 346 individuals were tested for SARS-CoV-2-specific antigen using either oral swabs or saliva. The overall seroprevalence of first-time-tested individuals was 12.6% during the first wave and 7.7% during the second wave (P < 0.01). Seroconversions and seroreversions within 6 months occurred at low rates, both below 5%. During the second wave, 3.5% of tested individuals were SARS-CoV-2 antigen positive, with two cases considered as re-infections. Severe clinical symptoms occurred in a greater proportion of cases during the first wave compared with the second wave (27.8% vs 10.6%, respectively; P = 0.03). Conclusion:The cumulative seroprevalence of SARS-CoV-2 antibodies in Madrid at the end of 2020 was approximately 20%. Seroreversions within 6 months occurred in 4% of cases. Seroconversions and reinfections were clinically less severe during the second wave than during the first wave. Hypothetically, a lower viral inoculum as a result of social distancing, increased use of face masks, promotion of outdoor activities and restrictions on gatherings may have contributed to this lower pathogenicity.

Frequency, risk factors, and outcomes of hospital readmissions of COVID-19 patients

“…In our study the association between glucocorticoid treatment and hospital readmission was remarkable. Since there was no generalized prescription of corticosteroids during the first wave, we cannot rule out that this treatment was a surrogate marker of greater pulmonary involvement predisposing to hospital readmission 25 . In addition, a positive association was found in the univariant analysis between macrolide treatment and a reduction in risk of hospital readmission.…”

SARS-CoV-2 Seroprevalence and Neutralizing Antibody Response after the First and Second COVID-19 Pandemic Wave in Croatia

“…In Germany (April–June 2020), seropositivity was 0.97% using ELISA, and 0.36% using VNT [ 20 ]. Significantly higher seropositivity was observed after the second pandemic peak, varying from 11.4% in Poland (October–November 2020) [ 21 ], and 19.3% in Spain (Madrid, at the end of 2020) [ 22 ], to 21.1% in Switzerland (Geneva, November–December 2020) [ 23 ]. In Slovenia, the seroprevalence after the first (April 2020) and second (October–November 2020) waves was found to be 2.78% and 4.06%, respectively [ 24 ].…”

Repeated Exposure to Subinfectious Doses of SARS-CoV-2 May Promote T Cell Immunity and Protection against Severe COVID-19

“…Despite the overall concern for the spread of the B.1.1.7 variant, which has been reported to cause a more severe illness as compared to previous SARS-CoV-2 viruses [ 1 , 2 , 3 ], COVID-19-associated mortality has not increased in parallel to the new surge of infections. Additionally, some studies performed in Italy and Spain observed a lower pathogenicity of COVID-19 in the second epidemic wave as compared to the first wave [ 4 , 5 ]. Several factors may have contributed to the current relative decrease in COVID-19 infection to mortality ratio as compared to the first wave.…”