Marginal cost: In economics and finance, marginal cost is the change in the total cost of increasing or decreasing a unit of output at a given level of output. Marginal cost is used to determine whether it is economically efficient to increase or decrease production. Theoretically, as output increases, marginal cost first decreases and then rises after a certain stage. That is, when production exceeds a certain limit, the total fixed cost increases. Therefore, the important factor affecting marginal cost is the stage increase of total fixed cost caused by the continuous expansion of production beyond a certain limit (production capacity). Uncertainty: Uncertainty is the degree of uncertainty about the measured value due to the presence of measurement error. In turn, it indicates the degree of trustworthiness of the result. It is an indicator of the quality of the measurement result. The smaller the uncertainty, the closer the said result is to the true value of the measured, the higher the quality, the higher the level, and the higher the value of its use; the larger the uncertainty, the lower the quality and the lower the level of the measured result, and the lower the value of its use. When reporting the results of physical quantity measurements, the corresponding uncertainty must be given to facilitate the assessment of its reliability by those who use it on the one hand, and to enhance the comparability between the measurements on the other. The HPV nine-valent vaccine has been officially available in the United States for more than a year (December 2014). Randomized controlled studies published in the NEJM have confirmed that the nine-valent vaccine has a good protective effect against HPV infections of subtypes 31/33/45/52/58 compared with the quadrivalent vaccine. Policy decisions on whether to switch from quadrivalent vaccination to a nine-valent vaccination program still need to balance health and economic benefits. A report published in JNCI evaluated this with a multitypeindividual-based transmission-dynamic model using HPV infection and disease (anogenital warts, anogenital tract and oropharyngeal cancers), a 3% discount rate, and sociological considerations. The model was calibrated with US sexual behavior and epidemiological data. The authors’ basic starting point was that the vaccine is 95% effective, has lifetime protection, and costs $145 and $158 per dose for quadrivalent and nine-valent vaccines, respectively. Predictive judgment was performed with simulated means (80% uncertainty interval [UI] = 10th to 90th interval). The results showed that the estimated costs for the quadrivalent vaccine gender-neutral vaccination schedule with and without cross-protection effects were $5,500 (80% UI = 2400-9400)/quality of life adjusted life year (QALY) and $7,300 (80% UI = 4300-11,000)/QALY, respectively. if translated to the nine-valent vaccine gender-neutral vaccination program, with or without cross-protective effects, there would be significant cost savings. The marginal cost/QALY gains (compared to boys vaccinated with the nine-valent vaccine/quadrivalent vaccine) with and without cross-protection effects were $140,200 (80% UI = 4200->1 million) and $31,100 (80% UI = 2100->1 million), respectively. These results remain positive after accounting for HPV natural history, screening methods, duration of protection, and health expenditures. It is worth noting that, if translated to a gender-neutral vaccination schedule for the nine-valent vaccine, the number of people vaccinated would need to be expanded to as many as six times in order to prevent an additional case of CIN2/3, HPV-associated cancer, or death. In summary, conversion from a quadrivalent to a nine-valent vaccination schedule would result in health economic cost savings if the additional cost per dose of the nine-valent vaccine was less than $13. Universal nine-valent vaccination of women in public health policy would provide the greatest socioeconomic benefit.