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Streptococcus pneumoniae is a leading cause of pneumonia and meningitis worldwide. Many different serotypes co-circulate endemically in any one location 1,2 . The extent and mechanisms of spread and vaccine-driven changes in fitness and antimicrobial resistance remain largely unquantified. Here using geolocated genome sequences from South Africa (n = 6,910, collected from 2000 to 2014), we developed models to reconstruct spread, pairing detailed human mobility data and genomic data. Separately, we estimated the population-level changes in fitness of strains that are included (vaccine type (VT)) and not included (non-vaccine type (NVT)) in pneumococcal conjugate vaccines, first implemented in South Africa in 2009. Differences in strain fitness between those that are and are not resistant to penicillin were also evaluated. We found that pneumococci only become homogenously mixed across South Africa after 50 years of transmission, with the slow spread driven by the focal nature of human mobility. Furthermore, in the years following vaccine implementation, the relative fitness of NVT compared with VT strains increased (relative risk of 1.68; 95% confidence interval of 1.59-1.77), with an increasing proportion of these NVT strains becoming resistant to penicillin. Our findings point to highly entrenched, slow transmission and indicate that initial vaccine-linked decreases in antimicrobial resistance may be transient., (© 2024. The Author(s).)

Psychological research shows that social comparison of individuals with peers or others shapes attitude formation 1,2 . Opportunities for such comparisons have increased with global inequality 3,4 ; everyday experiences can make economic disparities more salient through signals of social class 5,6 . Here we show that, among individuals with a lower socioeconomic status, such local exposure to inequality drives support for the redistribution of wealth. We designed a placebo-controlled field experiment conducted in South African neighbourhoods in which individuals with a low socioeconomic status encountered real-world reminders of inequality through the randomized presence of a high-status car. Pedestrians were asked to sign a petition to increase taxes on wealthy individuals to help with the redistribution of wealth. We found an increase of eleven percentage points in the probability of signing the petition in the presence of inequality, when taking into account the experimental placebo effect. The placebo effect suppresses the probability that an individual signs the petition in general, which is consistent with evidence that upward social comparison reduces political efficacy 4 . Measures of economic inequality were constructed at the neighbourhood level and connected to a survey of individuals with a low socioeconomic status. We found that local exposure to inequality was positively associated with support for a tax on wealthy individuals to address economic disparities. Inequality seems to affect preferences for the redistribution of wealth through local exposure. However, our results indicate that inequality may also suppress participation; the political implications of our findings at regional or country-wide scales therefore remain uncertain.