COVID-19 Breakthrough Infections and Transmission Risk: Real-World Data Analyses from Germany’s Largest Public Health Department (Cologne)

Abstract

Background and Methods: Vaccination is currently considered the most successful strategy for combating the SARS-CoV-2 virus. According to short-term clinical trials, protection against infection is estimated to reach up to 95% after complete vaccination (≥14 days after receipt of all recommended COVID-19 vaccine doses). Nevertheless, infections despite vaccination, so-called breakthrough infections, are documented. Even though they are more likely to have a milder or even asymptomatic course, the assessment of further transmission is highly relevant for successful containment. Therefore, we calculated the real-world transmission risk from fully vaccinated patients (vaccination group, VG) to their close contacts (CP) compared with the risk from unvaccinated reference persons matched according to age, sex, and virus type (control group = CG) utilizing data from Cologne’s health department. Results: A total of 357 breakthrough infections occurred among Cologne residents between 27 December 2020 (the date of the first vaccination in Cologne) and 6 August 2021. Of the 979 CPs in VG, 99 (10.1%) became infected. In CG, 303 of 802 CPs (37.8%) became infected. Factors promoting transmission included non-vaccinated status (β = 0.237; p < 0.001), male sex (β = 0.079; p = 0.049), the presence of symptoms (β = −0.125; p = 0.005), and lower cycle threshold value (β = −0.125; p = 0.032). This model explained 14.0% of the variance (corr. R2). Conclusion: The number of transmissions from unvaccinated controls was three times higher than from fully vaccinated patients. These real-world data underscore the importance of vaccination in enabling the relaxation of stringent and restrictive general pandemic control measures.

Analysis of a city‐wide COVID‐19 prevention strategy for aged‐care facilities during third and fifth waves of COVID‐19 in Kyoto City, Kyoto, Japan

“…It has been reported that elderly people lose vaccine antibodies more quickly and that the vaccine is less effective against variant strains 22 . Furthermore, Hsu et al previously reported that the number of transmissions from unvaccinated controls was three times higher than from fully vaccinated patients 22,23 . In our cohort, the number of cases identified within clusters decreased over, time and only one quarter of newly identified cases caused intra‐facility transmission.…”

School staff and teachers during the second year of COVID-19: Higher anxiety symptoms, higher psychological distress, and poorer mental health compared to the general population

“…In Spring 2020, when the data for the current study was collected, vaccination was only offered to adolescents aged 16 years and older ( Government of Canada, 2021 ). Thus, the majority of school staff were interacting with unvaccinated students, who were more likely to transmit COVID-19 than if they were vaccinated ( Hsu et al, 2021 ), which could have been an additional source of anxiety and stress for school staff.…”

COVID-19 Vaccination and Rates of Infections, Hospitalizations, ICU Admissions, and Deaths in the European Economic Area during Autumn 2021 Wave of SARS-CoV-2

“…This has mainly concerned the B.1.617.2 (delta) variant that was first identified in India in December 2020 and became dominant in the European Region by June/July 2021 [ 8 ]. A number of post-authorization studies originating from different countries in mid-2021 have shown that despite SARS-CoV-2 evolution, vaccination continues to decrease the risk of contracting the virus [ 2 , 9 , 10 , 11 ], while in the case of breakthrough infection, the risk of severe disease, hospitalization, and death is significantly reduced [ 12 , 13 , 14 , 15 ]. However, SARS-CoV-2, similarly to other respiratory viruses, reveals a strong seasonal pattern in the temperate zone, with infection rates rising in the autumn-winter season [ 16 , 17 , 18 ].…”