Obtaining a booster dose of coronavirus disease 2019 (COVID-19) vaccine is required to maintain the protective level of neutralizing antibodies and therefore herd immunity in the community, and the success of booster dose programs depends on public acceptance. The aim of this study was to determine the acceptance of a booster dose of COVID-19 vaccine and its drivers and barriers in Indonesia. A cross-sectional survey was conducted in the provinces of Indonesia between 1 and 15 August 2022. Individuals who completed the primary series of the COVID-19 vaccine were asked about their acceptance of a booster dose. Those who refused the booster dose were questioned about their reasons. A logistic regression was used to determine the determinants associated with rejection of a booster dose of COVID-19 vaccine. A total of 2935 respondents were included in the final analysis. With no information on the efficacy and safety of the COVID-19 vaccine, 95% of respondents agreed to receive a booster dose if it were provided for free by the government. This acceptance was reduced to only 50.3% if the vaccine had a 75% efficacy with a 20% chance of side effects. The adjusted logistic regression analysis indicated that there were eight factors associated with the rejection of the booster dose: age, marital status, religion, occupation, type of the first two vaccines received, knowledge regarding the importance of the booster dose, belief that natural immunity is sufficient to prevent COVID-19 and disbelief in the effectiveness of the booster dose. In conclusion, the hesitancy toward booster doses in Indonesia is influenced by some intrinsic factors such as lack of knowledge on the benefits of the booster dose, worries regarding the unexpected side effects and concerns about the halal status of the provided vaccines and extrinsic determinants such as the effectiveness and safety of the vaccine. These findings suggest the need for more campaigns and promotions regarding the booster dose benefits to increase its acceptance.

The pathophysiology and time course of impairment in cutaneous microcirculatory function and structure remain poorly understood in people with diabetes, partly due to the lack of investigational tools capable of directly imaging and quantifying the microvasculature in vivo. We applied a new optical coherence tomography (OCT) technique, at rest and during reactive hyperemia (RH), to assess the skin microvasculature in people with diabetes with foot ulcers (DFU, n = 13), those with diabetes without ulcers (DNU, n = 9), and matched healthy controls (CON, n = 13). OCT images were obtained from the dorsal part of the foot at rest and following 5 min of local ischemia induced by inflating a cuff around the thigh at suprasystolic level (220 mmHg). One-way ANOVA was used to compare the OCT-derived parameters (diameter, speed, flow rate, and density) at rest and in response to RH, with repeated-measures two-way ANOVA performed to analyze main and interaction effects between groups. Data are means ± SD. At rest, microvascular diameter in the DFU (84.89 ± 14.84 µm) group was higher than CON (71.25 ± 7.6 µm, P = 0.012) and DNU (71.33 ± 12.04 µm, P = 0.019) group. Speed in DFU (65.56 ± 4.80 µm/s, P = 0.002) and DNU (63.22 ± 4.35 µm/s, P = 0.050) were higher than CON (59.58 ± 3.02 µm/s). Microvascular density in DFU (22.23 ± 13.8%) was higher than in CON (9.83 ± 2.94%, P = 0.008), but not than in the DNU group (14.8 ± 10.98%, P = 0.119). All OCT-derived parameters were significantly increased in response to RH in the CON group (all P < 0.01) and DNU group (all P < 0.05). Significant increase in the DFU group was observed in speed ( P = 0.031) and density ( P = 0.018). The change in density was lowest in the DFU group (44 ± 34.1%) compared with CON (199.2 ± 117.5%, P = 0.005) and DNU (148.1 ± 98.4, P = 0.054). This study proves that noninvasive OCT microvascular imaging is feasible in people with diabetes, provides powerful new physiological insights, and can distinguish between healthy individuals and patients with diabetes with distinct disease severity.

Willingness to pay (WTP) for booster doses of coronavirus disease 2019 (COVID-19) vaccines is an under studied research topic. Therefore, the current study aimed to investigate the WTP for the booster doses of COVID-19 vaccines and its predictors in Indonesia using an online survey distributed all over the provinces of this low-middle-income country. The WTP was evaluated using a basic dichotomous contingent valuation approach, and its associated determinants were evaluated using a linear regression model. Out of 2935 responders, 66.2% (1942/2935) were willing to pay for a booster dose of the COVID-19 vaccine. The majority of respondents (63.5%) were willing to pay within a price range of 100,000–500,000 Indonesian rupiah (IDR), i.e., USD 6.71–33.57. Being older than 40 years, having a higher educational level, having a higher income, knowing and understanding that booster doses were important, and having a vaccine status that is certified halal (permissible in Islamic law), were all associated with a higher WTP for the booster dose of COVID-19 vaccines. The study findings imply that the WTP for a booster dose of COVID-19 vaccination in Indonesia is lower compared to acceptance of vaccines provided free of charge. This WTP data can be utilized to develop a pricing scheme for the booster doses of COVID-19 vaccination in the country with potential benefits in other low-income countries. The government may be required to provide subsidies for the herd immunity vaccination process to proceed as anticipated. Furthermore, the public community must be educated on the importance of vaccination as well as the fact that the COVID-19 epidemic is far from being over.

The mechanisms underlying reactive hyperemia (RH) responses in microvessels are poorly understood. Previous assessment tools have not been capable of directly visualising microvessels during physiological stimulation in humans. Optical coherence tomography (OCT) is capable of imaging and quantifying subcutaneous microvessels as small as ~30µm. In this study we use OCT to visualise and quantify skin microvascular changes in response to RH for the first time in humans. We also assessed the reproducibility of this technique. OCT and LDF were used simultaneously to scan cutaneous microvessels in 10 young healthy subjects on 2 days. We applied a speckle decorrelation algorithm to assess OCT images and calculated flow rate, speed, diameter and density parameters. Measures were obtained at rest (baseline) and 30-seconds following a 5-min cuff inflation (RH). All data were compared between days. The RH stimulus significantly increased (P<0.0001) OCT-derived microvascular diameter (37.6±3.4 vs 44.5±5.2µm), flow rate (82.4±23.4vs 240.1±58.6pl.s^-1), speed (48±5.7 vs 101.5±17.1µm.s^-1), density (5.1±1.7 vs 14.6± 2.6%) and also LDF-derived flux (12.3±5.7 vs 31.6±9.1 PU). At baseline, OCT-derived diameter (r=0.55), flow (r=0.64), speed (r=0.55) and density (r=0.75) showed significant between-day correlations (P <0.05), as did LDF results (r=0.74). In response to RH, OCT-derived diameter (r=0.63) and density (r=0.64) showed significant correlations (P<0.05), whereas flow (r=0.45), speed (r=0.43) and LDF (r=0.26) were less reproducible. Our study is novel in that it establishes the feasibility of using OCT to visualize and quantify microvascular structure and function responses to RH in humans.

Obesity has been proven to be the cause of various chronic diseases which can increase the risk of premature death. Changing lifestyle through diet and exercise is the best way to overcome the risk of obesity. This study aims to prove the effect of a combination of time-restricted feeding with moderate intensity aerobic exercise on increasing levels of myokines and improving body composition in obese women. A total of 28 obese women aged 20-30 years were involved in the study and were given time-restricted feeding (TRG) and time-restricted feeding and exercise (TREXG) interventions for 2 weeks. ELISA was used to measure PGC-1α and irisin levels in all samples, while TANITA DC-360 was used to measure body composition in the three groups TRG, TREXG, and the control group (CG). The results showed an increase in ∆PGC-1α between CG groups (0.25±2.29 ng/mL) vs TRG (1.64±3.56 ng/mL) vs TREXG (3.68±1.15 ng/mL) and p=0.031. ΔIrisin was also found to increase between CG (405.01±215.71 pg/mL) vs TRG (1443.92±1761.43 pg/mL) vs TREXG (3408.15±1299.85 pg/mL) and p=0.004. TREXG was found to have improved body composition compared to TRG and CG. The main finding of this study was an increase in myokines levels, namely levels of PGC-1α and irisin and there was an improvement in body composition in the time-restricted feeding and exercise group compared to the time restricted-feeding group and the control group in obese women. Keywords: Body composition, exercise, myokine, obesity, time-restricted feeding