How can we promote vaccination of the mass population?-Lessons from the COVID-19 vaccination defaults.

While vaccines are pivotal in combating COVID-19, concerns about side effects and complex procedures have hindered complete vaccination. Prior studies suggest that individuals defaulted to opt-out exhibit higher COVID-19 vaccination rates compared to those in opt-in systems. However, these studies were conducted in countries with a tolerant attitude towards vaccination and default changes, targeting specific age groups, and did not address potential deterrents like the increase in cancellation rates on the day, discomfort towards changing defaults, or the possibility of the opt-out effect being a one-time occurrence. Under the hypothesis that the default nature of the COVID-19 vaccination system influences attitudes towards vaccination even in countries conservative about vaccination and default changes like in Japan, we aimed to examine the differences in the first and second dose vaccination rates, cancellation rates, and the number of complaints between the opt-in and opt-out systems for COVID-19 vaccination. An email survey was conducted in 10 cities in A Prefecture, Japan. The results showed not only higher COVID-19 vaccination rates across all comparable age groups in the opt-out group but also a notably smaller decrease in the second-dose vaccination rate compared to the opt-in group, all achieved without any complaints about the system's introduction. Consequently, it can be inferred that the potential inhibiting factors were largely overcome. Despite some limitations, such as regional specificity, the study suggests that opt-out systems might increase COVID-19 vaccination coverage without leading to significant cancellations or complaints, presenting a promising strategy to facilitate vaccination efforts.

Sex-inducing effects toward planarians widely present among parasitic flatworms.

Various parasitic flatworms infect vertebrates for sexual reproduction, often causing devastating diseases in their hosts. Consequently, flatworms are of great socioeconomic and biomedical importance. Although the cessation of parasitic flatworm sexual reproduction is a major target of anti-parasitic drug design, little is known regarding bioactive compounds controlling flatworm sexual maturation. Using the planarian Dugesia ryukyuensis, we observed that sex-inducing substances found in planarians are also widespread in parasitic flatworms, such as monogeneans and flukes (but not in tapeworms). Reverse-phase HPLC analysis revealed the sex-inducing substance(s) eluting around the tryptophan retention time in the fluke Calicophoron calicophorum, consistent with previous studies on the planarian Bipalium nobile, suggesting that the substance(s) is likely conserved among flatworms. Moreover, six of the 18 ovary-inducing substances identified via transcriptome and metabolome analyses are involved in purine metabolism. Our findings provide a basis for understanding and modifying the life cycles of various parasitic flatworms.

Correction to: A comprehensive comparison of sex-inducing activity in asexual worms of the planarian Dugesia ryukyuensis: the crucial sex-inducing substance appears to be present in yolk glands in Tricladida.

[This corrects the article DOI: 10.1186/s40851-018-0096-9.].

A comprehensive comparison of sex-inducing activity in asexual worms of the planarian Dugesia ryukyuensis: the crucial sex-inducing substance appears to be present in yolk glands in Tricladida.

BACKGROUND: Turbellarian species can post-embryonically produce germ line cells from pluripotent stem cells called neoblasts, which enables some of them to switch between an asexual and a sexual state in response to environmental changes. Certain low-molecular-weight compounds contained in sexually mature animals act as sex-inducing substances that trigger post-embryonic germ cell development in asexual worms of the freshwater planarian Dugesia ryukyuensis (Tricladida). These sex-inducing substances may provide clues to the molecular mechanism of this reproductive switch. However, limited information about these sex-inducing substances is available. RESULTS: Our assay system based on feeding sex-inducing substances to asexual worms of D. ryukyuensis is useful for evaluating sex-inducing activity. We used the freshwater planarians D. ryukyuensis and Bdellocephala brunnea (Tricladida), land planarian Bipalium nobile (Tricladida), and marine flatworm Thysanozoon brocchii (Polycladida) as sources of the sex-inducing substances. Using an assay system, we showed that the three Tricladida species had sufficient sex-inducing activity to fully induce hermaphroditic reproductive organs in asexual worms of D. ryukyuensis. However, the sex-inducing activity of T. brocchii was sufficient only to induce a pair of ovaries. We found that yolk glands, which are found in Tricladida but not Polycladida, may contain the sex-inducing substance that can fully sexualize asexual worms of D. ryukyuensis. CONCLUSIONS: Our results suggest that within Tricladida, there are one or more common compounds or functional analogs capable of fully sexualizing asexual worms of D. ryukyuensis; namely, the crucial sex-inducing substance (hydrophilic and heat-stable, but not a peptide) produced in yolk glands.