Poliomyelitis prevention in the United States. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP).

These recommendations of the Advisory Committee on Immunization Practices (ACIP) for poliomyelitis prevention replace those issued in 1997. As of January 1, 2000, ACIP recommends exclusive use of inactivated poliovirus vaccine (IPV) for routine childhood polio vaccination in the United States. All children should receive four doses of IPV at ages 2, 4, and 6-18 months and 4-6 years. Oral poliovirus vaccine (OPV) should be used only in certain circumstances, which are detailed in these recommendations. Since 1979, the only indigenous cases of polio reported in the United States have been associated with the use of the live OPV. Until recently, the benefits of OPV use (i.e., intestinal immunity, secondary spread) outweighed the risk for vaccine-associated paralytic poliomyelitis (VAPP) (i.e., one case among 2.4 million vaccine doses distributed). In 1997, to decrease the risk for VAPP but maintain the benefits of OPV, ACIP recommended replacing the all-OPV schedule with a sequential schedule of IPV followed by OPV. Since 1997, the global polio eradication initiative has progressed rapidly, and the likelihood of poliovirus importation into the United States has decreased substantially. In addition, the sequential schedule has been well accepted. No declines in childhood immunization coverage were observed, despite the need for additional injections. On the basis of these data, ACIP recommended on June 17, 1999, an all-IPV schedule for routine childhood polio vaccination in the United States to eliminate the risk for VAPP. ACIP reaffirms its support for the global polio eradication initiative and the use of OPV as the only vaccine recommended to eradicate polio from the remaining countries where polio is endemic.     

The perspective of global eradication of poliomyelitis

In recent years, Germany and Switzerland have changed national policies to recommend vaccination with IPV (inactivated polio vaccine) instead of OPV (oral polio vaccine) for protection against poliomyelitis. An all IPV-schedule in routine childhood polio vaccination eliminates the - albeit minimal - risk of OPV-associated paralytic poliomyelitis. However, the impact of such a vaccination scheme on the goal to eventually eradicate poliomyelitis on a global level remains debatable. Published studies indicate that vaccine-derived poliovirus may persist in the environment for prolonged periods of time even after completion of a global eradication programme that relies on the near-exclusive use of OPV in the developing countries. Travellers vaccinated with IPV only might become silently infected with vaccine-derived virus, shedding it in large quantities. We therefore plead for a vaccination schedule that includes at least one last dose of OPV to induce strong mucosal immunity.     

脊髓灰质炎灭活疫苗基础免疫效果观察

目的 考察灭活脊髓灰质炎疫苗(inactivated poliomyelitis vaccine,IPV)在中国婴儿中的免疫效果,并与目前常规使用的口服脊髓灰质炎减毒活疫苗(oral poliomyelitis vaccine,OPV)进行比较.方法 对2个月龄婴儿采用组群随机法分为2个组,每组208名,分别接种IPV和OPV,并采集免疫前后血清.采用微量中和方法,对血清中抗脊髓灰质炎病毒3个型的中和抗体进行测定,对于抗体保护率比较采用X2检验进行统计学处理.抗体滴度进行对数转换后采用Z检验进行比较,所有统计学检验以P<0.05来确定差异是否具有统计学意义.结果婴儿经初次免疫后,IPV组Ⅰ、Ⅱ、Ⅲ型病毒中和抗体保护率分别为100.0%(186/186)、97.3%(181/186)、98.9%(184/186),几何平均滴度(GMT)分别为151.2、86.7、211.3,OPV组Ⅰ、Ⅱ、Ⅲ型病毒中和抗体保护率分别为97.4%(188/193)、100.0%(193/193)、95.3%(184/193),GMT分别为1089.5、538.2、203.7.两组中Ⅰ、Ⅱ型的保护率差异没有统计学意义(Ⅰ、Ⅱ型分别为X2Ⅰ=2.991,P=0.084;X2Ⅱ=3.512,P=0.061),但Ⅲ型中差异有统计学意义(X2Ⅱ=4.143,P=0.042).IPV组Ⅰ、Ⅱ型抗体几何平均滴度低于OPV疫苗,差异有统计学意义(ZⅠ=12.537,P=0.000;ZⅡ=13.415,P=0.000),而Ⅲ型抗体几何平均滴度差异没有统计学意义(ZⅢ=0.067,P=0.947).结论 经基础免疫后IPV在婴儿中免疫效果良好,和OPV相比,IPV组Ⅰ、Ⅱ型保护率与OPV相当,Ⅲ型高于OPV组.IPV组Ⅰ、Ⅱ型抗体几何平均滴度低于OPV疫苗,而Ⅲ型抗体几何平均滴度与OPV组相当.     

Oral poliomyelitis vaccine: time to change?

For 3 decades, vaccination against poliomyelitis has rested mainly on the use of the oral attenuated vaccine (OPV). In countries where wild type poliomyelitis has been successfully controlled by OPV, the rare cases of poliomyelitis that can still be identified occur in vaccinees or their contacts and are caused by vaccine related strains. Over years, data indicating that the inactivated vaccine (IPV) also has the potential to control poliomyelitis and that there are no known risks associated with the use of this vaccine have accumulated. The reasons for changes in vaccine policy in industrialised countries and the situation of the global effort of poliomyelitis immunisation are described. Some of the issues and challenges for the future are reviewed.     

Polio vaccination coverage and seroprevalence of poliovirus antibodies after the introduction of inactivated poliovirus vaccines for routine immunization in Japan

In Japan, the oral poliovirus vaccine (OPV) was changed to 2 types of inactivated poliovirus vaccine (IPV), the standalone conventional IPV (cIPV) and the Sabin-derived IPV combined with diphtheria-tetanus-acellular pertussis vaccine (DTaP-sIPV), for routine immunization in 2012. We evaluated polio vaccination coverage and the seroprevalence of poliovirus antibodies using data from the National Epidemiological Surveillance of Vaccine-Preventable Diseases (NESVPD) from 2011 to 2015. Several years before the introduction of IPV in 2012, OPV administration for children was refused by some parents because of concerns about the risk of vaccine-associated paralytic poliomyelitis. Consequently, in children aged <1?years who were surveyed in 2011–2012, polio vaccination coverage (45.0–48.8%) and seropositivity rates for poliovirus (type 1: 51.7–65.9%, type 2: 48.3–53.7%, and type 3: 15.0–29.3%) were decreased compared to those surveyed in 2009. However, after IPV introduction, the vaccination coverage (95.5–100%) and seropositivity rates (type 1: 93.2–96.6%, type 2: 93.1–100%, and type 3: 88.6–93.9%) increased among children aged <1?years in 2013–2015. In particular, seropositivity rates and geometric mean titers (GMTs) for poliovirus type 3 in <5-year-old children who received 4 doses of IPV (98.5% and 247.4, respectively) were significantly higher than in those who received 2 doses of OPV (72.5% and 22.9, respectively). Furthermore, in <5-year-old children who received 4 doses of either DTaP-sIPV or cIPV, the seropositivity rates and the GMTs for all 3 types of poliovirus were similarly high (96.5–100% and 170.3–368.8, respectively). Our findings from the NESVPD demonstrate that both the vaccination coverage and seropositivity rates for polio remained high in children after IPV introduction.     

Eradication of indigenous poliomyelitis in Canada: impact of immunization strategies

During the period 1950-1954, surveillance for paralytic poliomyelitis in Canada revealed an average of 1,914 cases (13.2 cases per 100,000) annually. The licensing and widespread use of inactivated poliovirus vaccine (IPV) in 1955 coincided with a marked decline in disease rates. Due to incomplete vaccine coverage of the population, a resurgence began in 1958 and peaked in 1959, despite an observed vaccine efficacy of 96% for 3 doses of IPV. The introduction and widespread use of oral poliovirus vaccine (OPV) started in 1960 and coincided with a decline in disease rates. Virtual elimination of the natural disease was achieved in the 1970s in all provinces regardless of the specific immunization program chosen (IPV or OPV alone or combined). From 1965 to 1988, 51 cases of paralytic poliomyelitis were reported in Canada. Thirty-five of these cases, all but one occurring before 1980, were attributed to wild virus infection, (14 caused by imported virus and 21 assumed to be endemic). Sixteen cases were OPV-associated: 4 in vaccine recipients and 12 in contacts of OPV recipients. Vaccine-associated paralysis in recipients and contacts occurred at the rate of one case per 9.5 million and 3.2 million vaccine doses distributed, respectively. The risk of paralysis attributable to OPV therefore is small compared to the overall benefit of the vaccine. Both IPV and OPV appear equally effective, and theoretically, a combination of the two (IPV followed by OPV) provides the best risk benefit ratio. Occasional exposure of the Canadian population to imported wild virus requires that high levels of population immunity be maintained.     

不同序贯程序的脊髓灰质炎灭活疫苗和减毒活疫苗的免疫效果研究

目的 评价脊髓灰质炎灭活疫苗（IPV）和减毒活疫苗（OPV）不同序贯免疫程序的免疫效果。方法 选取月龄≥2月的婴儿,分为1剂IPV和2剂OPV序贯组(I - O - O组)、2剂IPV和1剂OPV序贯组(I - I - O组)、IPV全程(I - I - I组)和OPV全程组(O - O - O),分别在2、3、4月龄时各接种1针,检测并比较各组人群血清中脊髓灰质炎中和抗体几何平均滴度（GMT）及抗体阳转率。结果 在完成基础免疫后,I - O - O 组Ⅰ、Ⅱ、Ⅲ型抗体GMT分别为948.78、930.91、955.08;I - I - O组抗体GMT分别为909.43、1 202.34、1 102.83;I - I - I 组GMT分别为333.02、298.56、411.98,O - O - O组抗体GMT分别为814.42、778.27、658.52;差异均有统计学意义;各组3个型别的抗体阳转率均为98％~100％,差异无统计学意义。接种1针IPV后脊髓灰质炎Ⅰ型、Ⅱ型、Ⅲ型中和抗体GMT分别为21.77、30.89、26.46,抗体阳转率分别为84.1％、91.5％、91.5％;接种第2剂IPV后,Ⅰ型、Ⅱ型、Ⅲ型中和抗体GMT分别69.42、133.89、212.58,抗体阳转率分别为100.0％、100.0％、99.9％。结论 IPV与OPV序贯接种后,对象产生的脊髓灰质炎中和抗体GMT比单独接种3剂IPV或3剂OPV高;不同序贯程序中,接种2剂IPV后抗体保护率较高。为了使机体产生更高的抗体水平并且避免疫苗相关麻痹病例发生,可采用IPV与OPV序贯程序,并以2剂IPV和1剂OPV的序贯程序为佳。     

The role of routine polio immunization in the post-certification era

The role of routine vaccination against poliomyelitis for the post-certification era remains an important area for policy decision-making. Two critical decisions need to be taken: first, to continue or discontinue vaccination with the live attenuated oral poliovirus vaccine (OPV); and second, if OPV is to be discontinued, whether vaccination with inactivated poliovirus vaccine (IPV) is needed. Four potential vaccination scenarios can be constructed: stop all polio vaccination; continue with current vaccination policies (OPV, IPV, or sequential schedule); discontinue OPV, but continue IPV universally; or discontinue OPV, but continue IPV in selected countries. All possible scenarios require continued investments in a surveillance and response strategy, including a stockpile of polio vaccine. Continuing vaccination would limit the savings that could be applied to the control of other health priorities. This report reviews the key issues associated with each scenario, highlights the advantages and disadvantages of each scenario, and outlines the major challenges for policy decision-making.     

A ten-year experience in control of poliomyelitis through a combination of live and killed vaccines in two developing areas.

We describe a successful program of poliomyelitis control using a combination of killed and live polio vaccines over a 10-year period in two developing areas, the West Bank and Gaza, adjacent to a relatively developed country, Israel. During the 1970s, immunization using live trivalent oral polio vaccine (OPV) in these areas covered more than 90 percent of the infant population. Nevertheless, the incidence of paralytic polio continued to be high, with many cases occurring in fully or partially immunized persons. It was thought that this could be due to interference with OPV take by other enteroviruses present in the environment due to poor sanitary conditions in these areas. A new policy combining five doses of OPV with two doses of inactivated polio vaccine (IPV) was adopted and implemented in 1978. In the 10 years since then, immunization coverage of infants increased to an estimated 95 percent and paralytic poliomyelitis has been controlled, despite exposure to wild poliovirus from neighboring countries including an outbreak in Israel in 1988. This experience suggests that wide coverage using the combination of IPV and OPV is an effective vaccination policy that may make eradication of polio possible even in developing areas.     

Live or inactivated poliomyelitis vaccine: an analysis of benefits and risks.

Using decision analysis we evaluated the benefits and risks of continued primary reliance on oral poliomyelitis vaccine (OPV) compared to use of inactivated poliovirus vaccine (IPV). We followed a hypothetical cohort of 3.5 million children from birth to age 30 assuming 95 per cent coverage with 98 per cent effective vaccine. Primary reliance on IPV would result in more cases of paralytic poliomyelitis as well as more susceptibles remaining in the population than would be expected with continuing OPV use (74.1 vs 10.0 cases and 5.9 per cent vs 1.1 per cent susceptibles, respectively). However, with OPV use, most cases of paralysis seen would be associated with the vaccine. Our analysis supports a continuation of current US policy placing primary reliance on OPV but the conclusion is heavily dependent on assumptions of risk of exposure to wild virus in the United States. Major declines in risk of exposure to wild virus could alter the balance significantly.     

Introduction of inactivated polio vaccine (IPV) into the routine immunization schedule of South Africa

South Africa is currently the only country on the African continent using inactivated polio vaccine (IPV) for routine immunization in a sequential schedule in combination with oral polio vaccine (OPV). IPV is a component of an injectable pentavalent vaccine introduced nationwide in April 2009 and administered according to EPI schedule at 6, 10 and 14 weeks with a booster dose at 18 months. OPV is administered at birth and together with the first IPV dose at 6 weeks, which stimulates gut immune system producing a memory IgA response (OPV), followed by IPV to minimize the risk of vaccine associated paralytic polio (VAPP). OPV is also given to all children under 5 years of age as part of regular mass immunizations campaigns. The decision to incorporate IPV into the routine schedule was not based on cost-effectiveness, which it is not. Other factors were taken into account: Firstly, the sequence benefits from the initial mucosal contact with live(vaccine) virus which promotes the IgA response from subsequent IPV, as well as herd immunity from OPV, together with the safety of IPV. Secondly, given the widespread and increasing use of IPV in the developed world, public acceptance of vaccination in general is enhanced in South Africa which is classified as an upper middle income developing country. Thirdly, to address equity concerns because of the growing use of IPV in the private sector. Fourthly, the advent of combination vaccines facilitated the incorporation of IPV into the EPI schedule.     

中国脊髓灰质炎疫苗使用历史回顾及免疫策略调整建议

在消灭脊髓灰质炎（脊灰）过程中,脊灰疫苗发挥了重要作用。口服脊灰减毒活疫苗（Oral Poliomyelitis Attenuated Live Vaccine,OPV）是一种安全有效的疫苗,中国于20世纪60年代推广使用OPV,常规免疫接种率逐步提高到〉90％。从1990年开始,部分省（自治区、直辖市）开展了OPV补充免疫活动（Supplementary Immunization Activity,SIA）;1993～2000年,开展消灭脊灰的国家免疫日活动,中国所在的世界卫生组织（World Health Organization,WHO）西太平洋区于2000年实现无脊灰的目标,继续在适龄儿童中加强OPV常规免疫和开展SIA。根据WHO制定的（（2013—2018年消灭脊灰终结战略计划》,2015年所有国家要引进至少1剂灭活脊灰病毒疫苗（Inactivated Poliovirus Vaccine,IPV）,2016年中期使用二价OPV（I＋Ⅲ型）,2018年停用OPV。为确保OPV成功转换IPV,中国应建立部门间协作机制,加快国产IPV研发生产进程,组织开展OPV和IPV转换的相关研究。     

Serological and virological assessment of oral and inactivated poliovirus vaccines in a rural population in Kenya.

A study was carried out in a rural community in Kenya to compare the humoral and intestinal immunity provided by three doses of oral poliovirus vaccine (OPV) and two or three doses of enhanced-potency inactivated poliovirus vaccine (IPV). The immunization series was started at 8-12 weeks of age and the interval between doses was 2 months. In children with low levels of maternal antibodies (i.e., those most at risk), the first dose of either vaccine stimulated antibody response. Children with high levels of maternal antibodies responded to the first dose of OPV, but not to that of IPV. Subsequent doses led to increases in the mean antibody titres with both vaccines. After three doses of OPV, the proportion of children with antibody titres of greater than or equal to 1:8 was 92% for type 1 virus, 98% for type 2, and 90% for type 3. After two doses of IPV the proportion of children with antibody titres of greater than or equal to 1:8 was 94%, 88%, and 97% for type 1, type 2, and type 3, respectively; after three doses of IPV, 100% of children had antibodies greater than or equal to 1:8 for types 1 and 3, and 98% for type 2. Intestinal immunity was tested with a challenge dose of type 1 OPV, but the dose used was too small to detect a significant difference between the vaccines.     

淮安市消灭脊髓灰质炎策略及效果分析

目的 评价淮安市消灭脊髓灰质炎防制策略效果。方法描述1956年以来脊髓灰质炎发病趋势；分析不同时期该病防制策略及发病特点。结果 随着脊灰疫苗的广泛使用和消灭脊灰活动的深入开展，淮安市脊灰发病率逐年下降，80年代脊灰发病开始得到有效控制，1995年以来已无确诊病例发生。主要防制策略是在常规免疫的基础上，开展强化免疫；加强免疫监测和急性弛缓性麻痹病例的监测。结论 淮安市已阻断了脊灰野病毒的传播；脊灰控制后，免疫策略应作相应调整，以控制疫苗相关病例的发生。     

Immunological priming of one dose of inactivated hepatitis A vaccine given during the first year of life in presence of maternal antibodies

BACKGROUND: In hepatitis A virus (HAV)-seronegative infants, inactivated hepatitis A vaccines are highly immunogenic. On the contrary, in infants who are HAV-seropositive before vaccination, the interfering effect of passively-transferred maternal anti-HAV antibodies leads to lower post-primary immunization anti-HAV levels, as compared to those achieved by seronegative infants. One possible way to overcome this drawback is to delay hepatitis A vaccination later during the first year of life. The objective of the study was to document the immunogenicity of an inactivated hepatitis A vaccine in 6 months old HAV-seropositive infants, given as two dose regimen consisting of a single primary immunization at 6 months of age, followed by a booster dose 6 months later. METHODS: The immunogenicity of one hepatitis A vaccine (Avaxim pediatric, Aventis Pasteur) was documented in 108 6 months old, HAV-seropositive infants randomly assigned to receive one priming dose of hepatitis A vaccine either concomitantly with (Group 2) or 2 weeks after the third dose of routine diphteria-tetanus-whole cell pertussis reconstituting lyophilized tetanus conjugated Haemophilus influenzae type b (DTwcP//PRP approximately T) vaccine and oral poliomyelitis vaccine (OPV) (Group 1). A booster dose was given 6 months later, concomitantly with MMR vaccine. RESULTS: The 91 infants who were HAV-seropositive (ELISA titer >20 mIU/ml) at the moment of primo vaccination remained seropositive 1 month later. Geometric mean titers (GMT) decreased from 292 and 278 mIU/ml 1 month after the first dose, to 77.6 and 76.0 mIU/ml 6 months after, in Groups 1 and 2, respectively. Post-booster titers increased markedly in both groups, with GMTs of 1731 and 1866 mIU/ml and geometric mean post/pre-immunization titer ratios of 22.3 and 24.6, respectively. CONCLUSIONS: These results suggest that immunological priming induced by a single dose of Avaxim pediatric administered to 6 or 6.5 months old, HAV-seropositive infants is present and should not preclude the use of this vaccine in such populations.     

Poliomyelitis: eradication in sight.

Eradication of poliomyelitis most likely will occur. In fact, it is almost gone from the Western Hemisphere. Health workers in Sweden, Finland, and the Netherlands routinely vaccinate almost all children with the inactivated poliovaccines (IPV). Despite good vaccination coverage, polio can still occur. For example, in 1978-1979, polio outbreaks occurred among people of closely knit interconnected religious groups in the Netherlands. The virulent type 1 poliovirus was imported from the Middle East and spread to related religious groups in Canada and U.S. Further, in 1984-1985, Finland experienced 10 polio cases. A wild type 3 variant was responsible. An outbreak in 1988 in Israel occurred among young adults who, although received the oral polio vaccine (OPV) as infants, did not receive booster doses. Thus they had an age related deficit in immunity against the wild virus. 6 countries in the Western Pacific Region were able to control polio by 1980, but wild type polioviruses were ubiquitous in 5 other countries in this region and infections were either asymptomatic or unrecognized. They could not control polio by 1980 and just recently able to exert some control. OPV induces serum antibodies, intestinal resistance, and rapid enduring immunity. Also it is easy to administer and inexpensive. Risk of paralytic polio with OPV is 1/1 million vaccinated infants. WHO advises that newborns should be immunized with OPV at the same time as BCG to protect them from polio and to reduce the transmission of wild polioviruses during infancy and childhood. Further many countries have incorporated OPV into routine immunization schedules, but can be difficult in developing countries with limited cold chain capabilities. While some developing countries host periodic mass OPV immunization campaigns. At proper doses, IPV imparts humoral immunity and can be incorporated into other injectable pediatric vaccines (e.g., DPT). Some countries use both IPV and OPV.     

Efficacy of oral poliovirus vaccine in rural communities of North Arcot District, India

The protective efficacy of three doses of oral poliovirus vaccine (OPV) was measured in children under five in the rural blocks of North Arcot District. In 1988, a sample survey of 7% of the total population of the district (population five million) was conducted to determine the immunization coverage with OPV and the incidence of paralytic poliomyelitis in under-fives in the previous 12 months, (n = 42,045). For every case of poliomyelitis, all children matched for exact age in months resident within the same block were taken as controls. Some 67 children had poliomyelitis (prevalence of lameness 1.59/1000, estimated annual incidence 2.57/1000 under-fives). Among cases and controls 24 and 42%, respectively, had received three doses of OPV, while 44 and 33% had received none. In a case-control analysis, the vaccine efficacy (VE) was 62% for all under-fives; for the 12-23 months age group it was 71.4%. For a vaccine with the potential of near 100% VE, this is disappointingly low. Obviously, not only the immunization coverage level, but also the VE should be enhanced if poliomyelitis is to be controlled in India. This may be achieved by a five-dose OPV schedule, annual OPV immunization campaigns in addition to the routine three-dose schedule or by using inactivated poliovirus vaccine of enhanced potency.     

脊髓灰质炎疫苗应用现状及免疫策略进展

1988年,全球消灭脊髓灰质炎（脊灰）倡议行动启动以来,取得了重大进展。2012年,全球报告脊灰223例,较2011年减少〉60%,本土脊灰流行国家减少为尼日利亚、巴基斯坦和阿富汗,脊灰野病毒（Wild Poliovirus,WPV）病例数下降到历史最低水平。但WPV传播仍未被阻断,无脊灰国家/地区仍面临输入WPV的风险。同时,有些国家正面临使用口服脊灰减毒活疫苗（Oral Poliomyelitis Attenuated Live Vaccine,OPV）所致疫苗衍生脊灰病毒的风险。目前,不同国家/地区评估各自的脊灰发病风险,依据OPV、脊灰病毒灭活疫苗（Inactivated Poliovirus Vaccine,IPV）的风险和收益,不同国家/地区采用不同的免疫策略：仅使用IPV、序贯使用IPV/OPV和仅使用OPV。2013年,世界卫生组织《全球消灭脊灰终结战略计划》中提出,2014年全球阻断WPV传播,2015年所有国家应至少使用1剂IPV,停用OPV中的Ⅱ型组分;2018年完成消灭WPV证实后,停用OPV。现对OPV和IPV的应用现状以及免疫策略进行简述。     

Cost analysis of post-polio certification immunization policies

OBJECTIVE: An analysis was conducted to estimate the costs of different potential post-polio certification immunization policies currently under consideration, with the objective of providing this information to policy-makers. METHODS: We analyzed three global policy options: continued use of oral poliovirus vaccine (OPV); OPV cessation with optional inactivated poliovirus vaccine (IPV); and OPV cessation with universal IPV. Assumptions were made on future immunization policy decisions taken by low-, middle-, and high-income countries. We estimated the financial costs of each immunization policy, the number of vaccine-associated paralytic poliomyelitis (VAPP) cases, and the global costs of maintaining an outbreak response capacity. The financial costs of each immunization policy were based on estimates of the cost of polio vaccine, its administration, and coverage projections. The costs of maintaining outbreak response capacity include those associated with developing and maintaining a vaccine stockpile in addition to laboratory and epidemiological surveillance. We used the period 2005-20 as the time frame for the analysis. FINDINGS: OPV cessation with optional IPV, at an estimated cost of US$ 20,412 million, was the least costly option. The global cost of outbreak response capacity was estimated to be US$ 1320 million during 2005-20. The policy option continued use of OPV resulted in the highest number of VAPP cases. OPV cessation with universal IPV had the highest financial costs, but it also had the least number of VAPP cases. Sensitivity analyses showed that global costs were sensitive to assumptions on the cost of the vaccine. Analysis also showed that if the price per dose of IPV was reduced to US$ 0.50 for low-income countries, the cost of OPV cessation with universal IPV would be the same as the costs of continued use of OPV. CONCLUSION: Projections on the vaccine price per dose and future coverage rates were major drivers of the global costs of post-certification polio immunization. The break-even price of switching to IPV compared with continuing with OPV immunizations is US$ 0.50 per dose of IPV. However, this doses not account for the cost of vaccine-derived poliovirus cases resulting from the continued use of OPV. In addition to financial costs, risk assessments related to the re-emergence of polio will be major determinants of policy decisions.     

Primary and booster vaccination with an inactivated poliovirus vaccine (IPV) is immunogenic and well-tolerated in infants and toddlers in China

IntroductionReplacing live-attenuated oral poliovirus vaccines (OPV) with inactivated poliovirus vaccines (IPV) is part of the global strategy to eradicate poliomyelitis. China was declared polio-free in 2000 but continues to record cases of vaccine-associated-poliomyelitis and vaccine-derived-poliovirus outbreaks. Two pilot safety studies and two larger immunogenicity trials evaluated the non-inferiority of IPV (Poliorix™, GSK Vaccines, Belgium) versus OPV in infants and booster vaccination in toddlers primed with either IPV or OPV in China.MethodsIn pilot safety studies, 25 infants received 3-dose IPV primary vaccination (Study A, www.clinicaltrial.gov NCT00937404) and 25 received an IPV booster after priming with three OPV doses (Study B, NCT01021293). In the randomised, controlled immunogenicity and safety trial (Study C, NCT00920439), infants received 3-dose primary vaccination with IPV (N = 541) or OPV (N = 535) at 2,3,4 months of age, and a booster IPV dose at 18-24 months (N = 470, Study D, NCT01323647: extension of study C). Blood samples were collected before and one month post-dose-3 and booster. Reactogenicity was assessed using diary cards. Serious adverse events (SAEs) were captured throughout each study.ResultsStudy A and B showed that IPV priming and IPV boosting (after OPV) was safe. Study C: One month post-dose-3, all IPV and ≥98.3% OPV recipients had seroprotective antibody titres towards each poliovirus type. The immune response elicited by IPV was non-inferior to Chinese OPV. Seroprotective antibody titres persisted in ≥94.7% IPV and ≥96.1% OPV recipients at 18–24 months (Study D). IPV had a clinically acceptable safety profile in all studies. Grade 3 local and systemic reactions were uncommon. No SAEs were related to IPV administration.ConclusionTrivalent IPV is non-inferior to OPV in terms of seroprotection (in the Chinese vaccination schedule) in infant and toddlers, with a clinically acceptable safety profile.