tetano
Editor, Senior Moderator
Emerg Infect Dis
. 2021 Dec 8;28(2).
doi: 10.3201/eid2802.211789. Online ahead of print.
Comparative Effectiveness of Coronavirus Vaccine in Preventing Breakthrough Infections among Vaccinated Persons Infected with Delta and Alpha Variants
Irina Kislaya, Eduardo Freire Rodrigues, Vítor Borges, João P Gomes, Carlos Sousa, José P Almeida, André Peralta-Santos, Baltazar Nunes, PT-COVID-19 Group2
Abstract
We developed a case-case study to compare mRNA vaccine effectiveness against Delta versus Alpha coronavirus variants. We used data on 2,097 case-patients with PCR-positive severe acute respiratory syndrome coronavirus 2 infections reported in Portugal during May-July 2021. We estimated the odds of vaccine breakthrough infection in Delta-infected versus Alpha-infected patients by using conditional logistic regression adjusted for age group and sex and matched by the week of diagnosis. We compared reverse-transcription PCR cycle threshold values by vaccination status and variant as an indirect measure of viral load. We found significantly higher odds of vaccine breakthrough infection in Delta-infected patients than in Alpha-infected patients (odds ratio 1.96 [95% CI 1.22-3.14]), suggesting lower effectiveness of the mRNA vaccines in preventing infection with the Delta variant. We estimated lower mean cycle threshold values for the Delta cases (mean difference -2.10 [95% CI -2.74 to -1.47]), suggesting higher infectiousness than the Alpha variant.
Keywords: Alpha variant; COVID-19; Delta variant; Portugal; SARS-CoV-2; breakthrough infections; coronavirus disease; mRNA vaccines; respiratory infections; severe acute respiratory syndrome coronavirus 2; vaccine-preventable diseases; viruses; zoonoses.
. 2021 Dec 8;28(2).
doi: 10.3201/eid2802.211789. Online ahead of print.
Comparative Effectiveness of Coronavirus Vaccine in Preventing Breakthrough Infections among Vaccinated Persons Infected with Delta and Alpha Variants
Irina Kislaya, Eduardo Freire Rodrigues, Vítor Borges, João P Gomes, Carlos Sousa, José P Almeida, André Peralta-Santos, Baltazar Nunes, PT-COVID-19 Group2
- PMID: 34876242
- DOI: 10.3201/eid2802.211789
Abstract
We developed a case-case study to compare mRNA vaccine effectiveness against Delta versus Alpha coronavirus variants. We used data on 2,097 case-patients with PCR-positive severe acute respiratory syndrome coronavirus 2 infections reported in Portugal during May-July 2021. We estimated the odds of vaccine breakthrough infection in Delta-infected versus Alpha-infected patients by using conditional logistic regression adjusted for age group and sex and matched by the week of diagnosis. We compared reverse-transcription PCR cycle threshold values by vaccination status and variant as an indirect measure of viral load. We found significantly higher odds of vaccine breakthrough infection in Delta-infected patients than in Alpha-infected patients (odds ratio 1.96 [95% CI 1.22-3.14]), suggesting lower effectiveness of the mRNA vaccines in preventing infection with the Delta variant. We estimated lower mean cycle threshold values for the Delta cases (mean difference -2.10 [95% CI -2.74 to -1.47]), suggesting higher infectiousness than the Alpha variant.
Keywords: Alpha variant; COVID-19; Delta variant; Portugal; SARS-CoV-2; breakthrough infections; coronavirus disease; mRNA vaccines; respiratory infections; severe acute respiratory syndrome coronavirus 2; vaccine-preventable diseases; viruses; zoonoses.