Spot speed cameras in a series - Effects on speed and traffic safety.

Reduced speeds and increased speed compliance are crucial for achieving increased road traffic safety, cutting across most Safe System interventions. Speed cameras have been shown to be effective in increasing speed compliance and reducing the number of fatalities and seriously injured. The speed cameras system in Sweden is different compared to many other countries, spot speed cameras are almost always placed in series along a road stretch. The aim of this study is to investigate the effects of this system on mean speeds, speed compliance, and on the number of fatalities and seriously injured. Including 20 years of data, the study applies before-after analysis to 361 speed measurement spots, and Empirical Bayes before-after analysis with control to crash outcomes on 202 road sections. The results show a mean speed decrease of 3.5 km/h for all vehicles and road sections, 7.9 km/h at cameras and 3.0 km/h between cameras. Furthermore, follow-up measurements showed that the effects were maintained long-term. Speed compliance increased 16 %-units, 42 %-units at cameras and 13 %-units between cameras. Though larger effects can be seen at cameras, there are still substantial effects on the enforced road sections between cameras. The cameras had an average effect of 38.6 % on decreasing fatalities and may also suggest a decrease for seriously injured, though not statistically significant. This study also shows that for roads that received both a decreased speed limit from 90 to 80 km/h and speed cameras, the mean speeds were reduced by additionally 3.6 km/h compared to roads with unchanged limits of 90 km/h. The combined effect on fatalities and seriously injured was a reduction by 61.6 % and 33.4 %. In conclusion, the Swedish strategy with spot speed cameras in a series led to an increased speed compliance and a comprehensive reduction in mean speeds and of the number of fatalities.

Cytotoxic T Cells Targeting Spike Glycoprotein Are Associated with Hybrid Immunity to SARS-CoV-2.

mRNA vaccination of individuals with prior SARS-CoV-2 infection provides superior protection against breakthrough infections with variants of concern compared with vaccination in the absence of prior infection. However, the immune mechanisms by which this hybrid immunity is generated and maintained are unknown. Whereas genetic variation in spike glycoprotein effectively subverts neutralizing Abs, spike-specific T cells are generally maintained against SARS-CoV-2 variants. Thus, we comprehensively profiled human T cell responses against the S1 and S2 domains of spike glycoprotein in a cohort of SARS-CoV-2-naive (n = 13) or -convalescent (n = 17) individuals who received two-dose mRNA vaccine series and were matched by age, sex, and vaccine type. Using flow cytometry, we observed that the overall functional breadth of CD4 T cells and polyfunctional Th1 responses was similar between the two groups. However, polyfunctional cytotoxic CD4 T cell responses against both S1 and S2 domains trended higher among convalescent subjects. Multimodal single-cell RNA sequencing revealed diverse functional programs in spike-specific CD4 and CD8 T cells in both groups. However, convalescent individuals displayed enhanced cytotoxic and antiviral CD8 T cell responses to both S1 and S2 in the absence of cytokine production. Taken together, our data suggest that cytotoxic CD4 and CD8 T cells targeting spike glycoprotein may partially account for hybrid immunity and protection against breakthrough infections with SARS-CoV-2.

Imprinted SARS-CoV-2-specific memory lymphocytes define hybrid immunity.

Immune memory is tailored by cues that lymphocytes perceive during priming. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic created a situation in which nascent memory could be tracked through additional antigen exposures. Both SARS-CoV-2 infection and vaccination induce multifaceted, functional immune memory, but together, they engender improved protection from disease, termed hybrid immunity. We therefore investigated how vaccine-induced memory is shaped by previous infection. We found that following vaccination, previously infected individuals generated more SARS-CoV-2 RBD-specific memory B cells and variant-neutralizing antibodies and a distinct population of IFN-γ and IL-10-expressing memory SARS-CoV-2 spike-specific CD4+ T cells than previously naive individuals. Although additional vaccination could increase humoral memory in previously naive individuals, it did not recapitulate the distinct CD4+ T cell cytokine profile observed in previously infected subjects. Thus, imprinted features of SARS-CoV-2-specific memory lymphocytes define hybrid immunity.