Objectives: To investigate the differences in vaccine hesitancy and preference of the currently available COVID-19 vaccines between two countries, namely, China and the United States (U.S.). Method: A cross-national survey was conducted in both China and the United States, and discrete choice experiments, as well as Likert scales, were utilized to assess vaccine preference and the underlying factors contributing to vaccination acceptance. Propensity score matching (PSM) was performed to enable a direct comparison between the two countries. Results: A total of 9077 (5375 and 3702 from China and the United States, respectively) respondents completed the survey. After propensity score matching, over 82.0% of respondents from China positively accepted the COVID-19 vaccination, while 72.2% of respondents from the United States positively accepted it. Specifically, only 31.9% of Chinese respondents were recommended by a doctor to have COVID-19 vaccination, while more than half of the U.S. respondents were recommended by a doctor (50.2%), local health board (59.4%), or friends and families (64.8%). The discrete choice experiments revealed that respondents from the United States attached the greatest importance to the efficacy of COVID-19 vaccines (44.41%), followed by the cost of vaccination (29.57%), whereas those from China held a different viewpoint, that the cost of vaccination covered the largest proportion in their trade-off (30.66%), and efficacy ranked as the second most important attribute (26.34%). Additionally, respondents from China tended to be much more concerned about the adverse effect of vaccination (19.68% vs. 6.12%) and have a lower perceived severity of being infected with COVID-19. Conclusion: Although the overall acceptance and hesitancy of COVID-19 vaccination in both countries are high, underpinned distinctions between these countries were observed. Owing to the differences in COVID-19 incidence rates, cultural backgrounds, and the availability of specific COVID-19 vaccines in the two countries, vaccine rollout strategies should be nation-dependent.

Some unusual phenomena besides near-infrared emission of Yb 3+ ions have been observed in ytterbiumdoped perovskite solid nanocrystals. A systematic study on doping kinetic and energy-transfer processes is presented. The observed unique dual-peak photoluminescence (PL) emission of perovskite nanocrystals in the visible region can be attributed to radiative recombination in the near-surface region and the interior region of the perovskite nanocrystals, respectively. Insightful studies based on dual-peak PL emission clarify the kinetic process of doping in perovskite nanocrystals. Once the dopant concentration of rare earth ions in the near-surface region is more than a certain value, the dopant ions start to immerse into the interior region of the host nanocrystals. The unusual excitation spectra of ytterbium-doped perovskite solid nanocrystals could be explained by the presence of two charge-transfer (CT) states at ∼24 000 cm −1 (CT1) and ∼21 460 cm −1 (CT2), and both of them could be observed in the near-surface region of the perovskite host. Furthermore, the lifetime of the near-infrared emission of Yb 3+ ions through the CT2 is three orders faster than that through CT1 (in millisecond), which should be fixed on the surface of the perovskite nanocrystals. The results provide essential insights into the dynamic carrier behaviors and surface effects of all inorganic perovskite nanocrystals doped with rare earth ions for expanded functionality.

No abstract