High rates of vaccine hesitancy among pregnant women during the coronavirus disease 2019 (COVID-19) pandemic in Japan.

This study aimed to 1) determine the prevalence and contents of vaccine hesitancy among pregnant women during the coronavirus disease 2019 (COVID-19) pandemic and 2) evaluate its association with maternal sociodemographic factors. A cross-sectional survey was conducted between August and December 2020 among pregnant women between 28 and 32 weeks of gestation who received antenatal care at four clinics and hospitals in Niigata City, Japan. Vaccine hesitancy was assessed using the Parent Attitudes about Childhood Vaccines survey, and associations between vaccine hesitancy and sociodemographic factors were analyzed. In total, 113/200 (56.5%) subjects responded to the survey. Overall, 46/113 (40.7%) pregnant women were resistant or hesitant to receive the vaccine. Women with vaccine hesitancy were more likely to fear adverse reactions (concern 79.6%, not concerned 15.9%, and not sure 4.4%), safety (concerned 69.0%, not concerned 23.9%, and not sure 7.1%), and efficacy (concerned 47.8%, not concerned 35.4%, and not sure 16.8%) compared to those without vaccine hesitancy (P < .01, < .01, and <.01, respectively). In the multivariate logistic regression analyses, primipara women had higher rates of vaccine hesitancy than multipara pregnant women (odds ratio: 2.38, P = .04). In conclusion, the prevalence of vaccine hesitancy among pregnant Japanese women, especially primipara women, was higher than that in other countries during the COVID-19 pandemic. Their major concerns were adverse reactions, safety, and the efficacy of childhood vaccines. Further strategies are needed to provide appropriate vaccine information to prevent vaccine-preventable diseases in both infants and children.

High-pressure glass formation of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide homologues.

We investigated the stability of the liquid phase of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cnmim][TFSI]) homologues with different alkyl chain lengths for 3 ≤ n ≤ 10 at room temperature. We found that all [Cnmim][TFSI] samples (n = 3-10) formed a glassy state when pressure was applied. Intriguingly, the glass transition pressure (pg) slightly increases up to n = 5, reaches a plateau at n ≧ 8, and increases again at n = 10. This is completely different from the high-pressure glass formation of [Cnmim][BF4], where the pg decreases as n increases. We discussed the local structural changes occurring in [Cnmim][TFSI] in view of the conformational changes of the cation and anion, and small-angle X-ray scattering data. It seems that [Cnmim][TFSI] is resistant to external pressure and retains its local liquid structure by conformational adjustments of the cation and anion.

Low-temperature and high-pressure phases of a room-temperature ionic liquid and polyiodides: 1-methyl-3-propylimidazolium iodide.

Using simultaneous small-angle X-ray scattering (SAXS) combined with differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) combined with DSC measurements, low-temperature (LT) solid phases of a room-temperature ionic liquid (RTIL) and its mixtures were examined at ambient pressure. The considered RTIL was 1-methyl-3-propylimidazolium iodide ([C3mim][I]), and the mixtures could be expressed as [C3mim][Im]. Under high-pressure (HP), the crystallization of pure [C3mim][I] was suppressed, as a LT-amorphous form of pure [C3mim][I] was formed. In the mixed system, the HP crystallization of [C3mim][I3] occurred at 0.95 GPa of compression. In [C3mim][I3.66] as a non-stoichiometric system, complicated phase changes were observed. Upon compression, the edge of a sample container was crystallized. By further compression, a crystal-crystal phase transition was observed as a HP-crystal polymorph appeared. In the centre, HP amorphization was observed upon compression, whereas decompression crystallization was induced by decreasing the pressure. The HP complicated behaviors of non-stoichiometric [C3mim][I3.66] are caused by the excess of iodide/iodine.

Stability of the Liquid State of Imidazolium-Based Ionic Liquids under High Pressure at Room Temperature.

To understand the stability of the liquid phase of ionic liquids under high pressure, we investigated the phase behavior of a series of 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cnmim][BF4]) homologues with different alkyl chain lengths for 2 ≤ n ≤ 8 up to ∼7 GPa at room temperature. The ionic liquids exhibited complicated phase behavior, which was likely due to the conformational flexibility in the alkyl chain. The present results reveal that [Cnmim][BF4] falls into superpressed state around 2-3 GPa range upon compression with an implication of multiple phase or structural transitions to ∼7 GPa. Remarkably, a characteristic nanostructural organization in ionic liquids largely diminishes at the superpressed state. The behaviors of imidazolium-based ionic liquids can be classified into, at least, three patterns: (1) pressure-induced crystallization, (2) superpressurization upon compression, and (3) decompression-induced crystallization from the superpressurized glass. Interestingly, the high-pressure phase behavior was relevant to the glass transition behavior at low temperatures and ambient pressure. As n increases, the glass transition pressure (pg) decreases (from 2.8 GPa to ∼2 GPa), and the glass transition temperature increases. The results indicate that the p-T range of the liquid phase is regulated by the alkyl chain length of [Cnmim][BF4] homologues.