수두 2회 예방접종의 비용-편익 분석

Abstract

[한글]

수두는 전염력이 매우 강한 전염병임에도 불구하고 2005년에야 법정전염병에 포함되고 국가필수예방접종으로 선정되었다. 현재 우리나라에서는 만 12~15개월에 1회의 예방접종을 권장하고 있다. 하지만 미국에서는 1회 예방접종 후에도 수두 유행이 지속적으로 발생하여 2006년 6월 생후 12~15개월에 1차, 만 4~6세에 2차 접종을 할 것을 권장하고 있다. 우리나라에서는 수두 예방접종 사업의 경제성 평가가 미비하여 2차 접종 도입을 고려할 근거가 부족하다. 따라서 본 연구를 통해 우리나라에서의 수두 2회 예방접종의 비용-편익을 분석하여 어떠한 사업이 경제적 효율성이 높은지 평가해 보고자 한다.

수두 예방접종 전략은 1회 접종 전략(생후 12~15개월)과 2회 접종 전략(생후 12~15개월, 만 4~5세)으로 구분하였으며, 각각 비용과 편익을 세분화하여 금전적 가치로 환산한 다음 그 값을 미접종 시와 비교, 전략간 비교를 실시하였다.

수두 예방접종의 비용-편익 분석을 위해 의사결정 모델을 이용하여 2007년 출생 코호트를 대상으로 향후 20년간 발생할 수두 예방접종 비용과 수두 발생 예방을 통해 얻을 수 있는 편익을 비교하였다. 수두 예방접종 비용은 민간 의료기관(60%)과 공공 의료기관(40%)을 구분하여 각각 직접비용과 간접비용을 산출하였다. 직접비용에는 백신비용과 의료행위에 대한 가치가 포함되고, 간접비용은 예방접종을 위해 의료기관 방문 시 소요되는 시간비용과 교통비가 포함된다. 수두 예방접종을 통해 얻을 수 있는 편익을 위해서는 향후 20년간 발생할 수두 환자 수 예측이 필요하다. 환자 수 예측 모델은 캐나다에서 시행한 미분 방정식에 기본을 둔 수학적 모델을 이용하였고, 예방접종을 하지 않았을 때와 1회 시행하였을 때, 2회 시행하였을 때 20년간 예측되는 수두 환자 발생을 각각 추계하였다. 이렇게 산출된 환자 수에 수두 환자 1인당 치료비용을 곱하여 편익을 계산하였다. 편익은 직접편익과 간접편익으로 나누어 산출하였고, 직접편익에는 수두와 수두 합병증으로 인한 입원, 외래 진료비가 포함되고, 간접편익은 수두 치료를 위한 교통비와 시간비용이 포함된다.

수두 예방접종 정책별 향후 20년간 수두 환자 수 추정 결과, 수두 예방접종 사업을 미실시할 경우 2007년 출생코호트 449,027명 중 2007~2026년까지 총 369,098명의 수두 환자가 발생하는 것으로 예측되었다. 12~15개월에 수두 예방접종을 1회 실시하는 전략 1(1차 접종률 87.8%)의 경우 70,696명의 환자가 발생하는 것으로 예측되었고, 12~15개월과 4~6세에 수두 예방접종을 2회 실시하는 전략 2(1차 접종률 87.8%, 2차 접종률 51.7%)의 경우 20년간 수두 환자 수는 34,253명이였다.

수두 예방접종률에 변화를 주어 수두 환자 수를 추정해 본 결과 2차 접종을 1차 접종률과 같다고 가정하였을 때 수두 환자 수는 32,253명으로 감소하였다. 접종률을 기억에 의한 MMR 접종률과 같이 1차 98.1%, 2차 58.0%로 변화시켰을 때 수두 환자 수는 32,936명으로 1, 2차 모두 87.8%의 접종률을 유지하였을 때보다 오히려 환자 발생이 늘어났다.

2007년 출생 코호트가 예방접종을 1회 실시할 경우 총 142억의 비용이 소요되고, 예방접종을 2회 실시할 경우 225억의 비용이 소요된다. 미접종과 비교 시 1회 접종 전략은 총 30만 명이 수두에 걸리지 않게 되었고, 이로 인해 212억의 수두 치료비용을 감소시켰다. 편익-비용비가 1.49로 나타났으며 순편익은 69억 발생하였다. 미접종과 비교 시 2회 접종 전략은 총 33만 명이 수두에 걸리지 않게 되었고, 236억의 수두 치료비용을 절감시켰으며, 편익-비용비가 1.05, 순편익은 109억원 발생하였다. 다시 말해 수두 예방접종을 시행하지 않는 것보다 1회 접종 전략과 2회 접종 전략은 모두 비용편익적인 것으로 나타났다.

1회 접종 전략과 2회 접종 전략을 비교하였을 때 만 4~6세에 2차 예방접종을 시행할 경우 1차만 시행하였을 때보다 총 4만 명이 수두에 걸리지 않게 되었고, 이로 인해 25억의 수두 치료비용을 감소시켰다. 편익-비용비가 0.30으로 나타났으며 순편익은 -58억 발생하여 1회 접종보다 경제성이 없음을 알 수 있다.

결론적으로 현재 우리나라에서 수두 예방접종의 시행은 경제성이 있으나, 2회 접종의 시행은 비용의 증가에 비해 편익이 크지 않은 것으로 나타났다. 우리나라의 수두 유행 상황과 국가 예방접종 정책 변화에 따라 2회 수두 예방접종정책 도입 여부는 신중히 판단하여야 할 것이다.

[영문]

Despite the fact that varicella is a contagious disease with strong infectivity, it was listed as a legal communicable disease, and designated as NIP(National Immunization Program) only in 2005. Presently, it is recommended that infants are to be vaccinated one time when they are 12-to-15-month old in Korea. However, in the United States, it is recommended that the infants get first at age 12 to 15 months, and the second vaccination between four and six years of age from June 2006, for varicella has prevailed even after one-time vaccination. In Korea, there lacks a basis to consider introduction of the second vaccination, due to insufficient evaluation of economical efficiency in relation to varicella vaccination. Therefore, this research aims at evaluating which business strategy would have a higher economical efficiency by analyzing cost-benefit of the second varicella vaccination in Korea.

Varicella vaccination strategy was divided into one-time vaccination strategy (for infants at age 12 to 15 months) and two-time vaccination strategy (for infants at age 12 to 15 months, also toddlers between four and five years of age). Each strategy’s cost and benefit was specified and then converted into monetary value. And this value was compared to the one derived from the case of non-vaccination. The comparisons were also made between the two strategies.

To analyze the cost-benefit of varicella vaccination, cohort of infants born in 2007 was selected, and the costs of varicella vaccination that would be accrued for the next 20 years and the benefits that would be able to obtain through prevention of occurrence of varicella were compared by using a decision-making model. Direct and indirect expenses of the varicella vaccination were calculated by dividing them into the portion for civilian medical institution (60%) and for public medical institution (40%). Vaccine costs and the value related to medical practice were included in the direct expense, and time-consuming costs and transportation expenses that would incur when visiting a medical institution were included in the indirect one. To figure out benefits that may be gained through varicella vaccination, it is necessary to predict the number of patients would occur for the next 20 years. A mathematical model based on the differential equation developed in Canada was used as the prediction model for number of patients. And the occurrence of patients being predicted for the next 20 years when vaccination has not been performed, when one-time and two-time vaccinations have been performed, were estimated respectively. And benefits were calculated by multiplying the number of patients that calculated by the treatment expense per patient infected with varicella. Benefits were calculated by dividing them into direct benefits and indirect benefits. Expense for hospitalization, as well as the expense to visit a hospital as an outpatient was included in the direct benefits, and transportation expenses and time-consuming costs to treat varicella were included in the indirect ones.

The results from estimation of the patients for the next 20 years by the varicella vaccination strategy as follows: when varicella vaccination project has not been performed, total 369,098 patients would occur among 449,027 young children-the cohort of infants born in 2007, up until 2007 to 2026. In case of strategy 1 (the rate of first vaccination, 87.8%) that performs one-time vaccination against varicella for 12-to-15-month baby, it was predicted that 70,696 patients would occur, and in case of strategy 2 (the first vaccination rate, 87.8%; the second vaccination rate, 51.7%) that performs two-time vaccination at age 12 to 15 months, and also between four and six years of age, the number of patients was 34,253.

The results from prediction of the number of patients, giving changes in the rate of vaccination were as follows. When assuming the second vaccination rate was same as the first one, the number of patients was reduced to 32,253. When changing the vaccination rate, like MMR vaccination rate by memory, into 98.1% for the first vaccination, and into 58.0% for the second one, the number of patients was 32,936, and the patience occurrence was rather increased than when the vaccination rate was maintained at 87.8% for both first and second vaccination.

In case that the cohort of infants born in 2007 are vaccinated one time, total 14.2 Billion Won shall be required for their vaccination, and in case that vaccination is performed two times, total 22.5 Billion Won shall be required. When comparing to non-vaccination, total 300 thousand people could be vaccinated against varicella under one-time vaccination strategy. For this reason, varicella treatment expense of 21.2 Billion Won was reduced. The ratio of benefit-cost was 1.49, and net benefit was 6.9 Billion Won. When comparing to non-vaccination, total 330 thousand people were immune to varicella owing to the two-time vaccination strategy. As a result, it cuts down varicella treatment expenses of 23.6 Billion Won. The ratio of benefit-cost was 1.05, and net benefit was 10.9 Billion Won. In other words, one-time and two-time vaccination strategy both showed more cost beneficial than the case of non-vaccination.

When comparing the two strategies, in case of performing the second vaccination at age four to six years, total four Million people more than that of one-time vaccination could be immune to varicella. Because of this, the varicella treatment expense of 2.5 Billion Won was decreased. The ratio of benefit-cost was 0.30, and the net benefit was -5.8 Billion Won, and this indicates that two-time vaccination is less economical efficiency than one-time vaccination.

In conclusion, performance of vaccination against varicella in Korea showed economical efficiency, however, two-time vaccination indicated that the benefit is not greater than the portion of the increase of expenses. Therefore, the introduction of two-time vaccination shall be carefully determined considering the prevalence of varicella in Korea, and changes in national vaccination policy.