ABSTRACT
Early evidence suggests that the COVID-19 pandemic may have reduced the proportion of individuals submitted to cervical, colorectal and breast cancer screening. However, the recovery from the pandemic impact was very heterogeneous. We aim to explore the impact of the pandemic on cancer screening and estimate the time to recover lost screening opportunities in Portugal. We used an interrupted time series to analyze the impact of the pandemic on the implementation of cancer screening. The study population was the eligible individuals screened for cervical, colorectal and breast cancer by month and health region between 2018 and 2021. We used Poisson regression with health region random effects to estimate the trend before and after the first lockdown (March 2020) and the impact of the first lockdown. We predicted the counterfactual evolution without a pandemic to estimate lost screening opportunities. The first lockdown resulted in 93,1% (95%CI 92,9-93,2), 89,4% (95%CI 89,2-89,5) and 84,1% (95%CI 83,8-84,3) decrease in the proportion of expected cervical, colorectal and breast cancer screening tests. Nonetheless, we document an increased trend difference between pre and post lockdown of 6,0% (95%CI 5,9-6,0) and 5,3% (95%CI 5,3-5,4), 3,7% (95%CI 3,6-3,7) per month. However, by December 2021, there are still many lost screening opportunities due to the pandemic - 293k cervical cytology tests (42,2% less than expected), 247k fecal occult blood tests (28,7%) and 388k mammograms (38,4%). The first lockdown resulted in an abrupt decrease in cancer screening. However, we document an increase in the cancer screening trend after the pandemic. Nevertheless, there are still considerable lost screening opportunities after 2 years. Key messages • The pandemic caused a massive disruption in cancer screening. Although there was an increase in screening trends after the first lockdown, 2 years later, many lost screening opportunities remain. • Population-based screenings need to increase the outputs to account for lost screening opportunities due to the pandemic.
ABSTRACT
Introduction Vaccination is the primary pharmacological measure to reduce SARS-CoV-2 transmission and its complications. Timely information on vaccines effectiveness in a context of novel variants of concern (VOC) emergence is essential for public health policies. This study aimed to provide a measure of comparative vaccine effectiveness between Omicron (BA.1) and Delta (B.1.627.2) VOC according to vaccination exposure (complete primary regimen or booster dose) for Portuguese population aged 12 or more years old using routinely collected data from electronic health records. Methods We used a case-case study design linking national electronic vaccination registry and surveillance data on 13,134 SARS-CoV-2 RT-PCR laboratory-confirmed cases notified in Portugal during weeks 49-51 of 2021. Notified cases were classified as Omicron or Delta based on whole-genome sequencing or S-gene Target Failure (SGTF) status using the RT-PCR TaqPath™ Covid 19 CE IVD Kit (Thermo Scientific™) assay. The odds of vaccination was compared between Omicron cases and Delta cases using logistic regression adjusted for age group, sex, region and week of diagnosis and laboratory of origin. Results The odds of vaccination were higher in laboratory-confirmed cases infected by Omicron (BA.1) VOC compared to Delta (B.1.627.2) VOC for both complete primary vaccination (Odds ratio (OR)=2.1;95% Confidence Interval (95%CI): 1.8 - 2.4) and booster dose (OR = 5.2;95%CI: 3.1 - 8.8), indicating vaccine effectiveness reduction against Omicron. Conclusions We found significantly higher odds of vaccination in Omicron cases compared to Delta, suggesting lower effectiveness of the primary vaccination and the booster dose in preventing infections by Omicron. Case-case study design has proven to be feasible approach to rapidly compare vaccine effectiveness between VOC in context of novel VOC emergence to timely inform public health stakeholders. Key messages • Reduction of vaccine-induced protection against SARS-COV-2 infection with the Omicron compared to Delta after primary and booster vaccination. • Continuous monitoring of COVID-19 vaccine effectiveness is essential to support public health policies in context of novel VOC emergence.