Surveillance for poliovirus vaccine adverse events, 1991 to 1998: impact of a sequential vaccination schedule of inactivated poliovirus vaccine followed by oral poliovirus vaccine

Use of Inactivated Polio Vaccine Among U.S. Adults: Updated Recommendations of the Advisory Committee on Immunization Practices - United States, 2023

Poliovirus can cause poliomyelitis and lifelong paralysis. Although wild poliovirus types 2 and 3 have been eradicated, wild poliovirus type 1 and vaccine-derived polioviruses are still circulating in multiple countries worldwide. In 2022, a case of paralytic polio caused by vaccine-derived poliovirus type 2 was identified in an unvaccinated young adult in New York. This case and subsequent detection of community transmission underscored the ongoing risk for importation of poliovirus into the United States and risk for poliomyelitis among unvaccinated persons. However, previous Advisory Committee on Immunization Practices (ACIP) recommendations for adult polio vaccination were limited to adults known to be at increased risk for exposure. During October 2022-June 2023, the ACIP Polio Vaccine Work Group reviewed data on poliovirus surveillance and epidemiology, safety and effectiveness of inactivated poliovirus vaccine (IPV), and other considerations outlined in the ACIP Evidence to Recommendations Framework. On June 21, 2023, ACIP voted to recommend that all U.S. adults aged ≥18 years who are known or suspected to be unvaccinated or incompletely vaccinated against polio complete a primary polio vaccination series with IPV. This report summarizes evidence considered for this recommendation and provides clinical guidance for the use of IPV in adults.

Surveillance of acute flaccid paralysis and poliomyelitis on some territories of Russia and South Viet Nam. Part 1. Polioviruses and paralysis

The epidemiological and etiological aspects of poliomyelitis and acute flaccid paralysis (AFP) in Russia and Vietnam were analysed and compared. The polio-free status is maintained on 14 territories of Russia and 29 provinces of South Vietnam. The quality of epidemiological and virological surveillance for acute flaccid paralysis is in accordance with the requirements of the national and international polio surveillance systems. All AFP cases were revealed, registered, reported and investigated in both countries. The percentage of poliovirus isolation from 2,492 samples collected from patients with acute flaccid paralysis and contact persons in different years in Russia ranged from 1.30.89 to 9.80.79. In South Vietnam, 2,143 samples from patients with acute flaccid paralysis were investigated. In Russia and Vietnam, we isolated vaccine polioviruses of all three types with predominance of type 3 polioviruses (63% and 50%, respectively) in both countries. From AFP patients in Russia and Vietnam, polioviruses were isolated in 4.9% and 1.0% studied samples, respectively. Some VDPV strains were revealed on the territories of Russia and South Vietnam. Here, we describe five cases of vaccine-associated paralytic poliomyelitis registered in Russia and two cases of AFP caused by VDPV type 2 reported in Vietnam. To prevent the risk of developing vaccine-associated paralytic poliomyelitis, it is indispensable to ensure high-quality surveillance for acute flaccid paralysis, maintain 95% polio vaccine pediatric coverage and strictly comply with sanitary legislation, including the National Vaccination Schedule when vaccinating children, to improve virological surveillance of polioviruses using classical and new virological and molecular methods and to continue research on poliomyelitis, including development of new safe and effective poliovirus vaccines able to induce both humoral and mucosal immunity. The systematic control of adequate polio vaccination is indispensable in order to prevent transmission of imported wild polioviruses into polio free countries as well as circulation of vaccine-derived polioviruses worldwide.

Mucosal COVID-19 vaccines: Risks, benefits and control of the pandemic

Based on mucosal immunization to promote both mucosal and systemic immune responses, next-generation coronavirus disease 2019 (COVID-19) vaccines would be administered intranasally or orally. The goal of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines is to provide adequate immune protection and avoid severe disease and death. Mucosal vaccine candidates for COVID-19 including vector vaccines, recombinant subunit vaccines and live attenuated vaccines are under development. Furthermore, subunit protein vac-cines and virus-vectored vaccines have made substantial progress in preclinical and clinical settings, resulting in SARS-CoV-2 intranasal vaccines based on the previously successfully used nasal vaccines. Additional to their ability to trigger stable, protective immune responses at the sites of pathogenic infection, the development of 'specific' mucosal vaccines targeting coronavirus antigens could be an excellent option for preventing future pandemics. However, their efficacy and safety should be confirmed.

Cost-Effectiveness of Three Poliovirus Immunization Schedules in Shanghai, China

In Shanghai, China, a polio immunization schedule of four inactivated polio vaccines (IPV) has been implemented since 2020, replacing the schedules of a combination of two IPVs and two bivalent live attenuated oral polio vaccines (bOPV), and four trivalent live attenuated oral polio vaccines (tOPV). This study aimed to assess the cost-effectiveness of these three schedules in infants born in 2016, in preventing vaccine-associated paralytic poliomyelitis (VAPP). We performed a decision tree model and estimated incremental cost-effectiveness ratio (ICER). Compared to the four-tOPV schedule, the two-IPV-two-bOPV schedule averted 1.2 VAPP cases and 16.83 disability-adjusted life years (DALY) annually; while the four-IPV schedule averted 1.35 VAPP cases and 18.96 DALY annually. Consequently, ICER_VAPP and ICER_DALY were substantially high for two-IPV-two-bOPV (CNY 12.96 million and 0.93 million), and four-IPV (CNY 21.24 million and 1.52 million). Moreover, net monetary benefit of the two-IPV-two-bOPV and four-IPV schedules was highest when the cost of IPV was hypothesized to be less than CNY 23.75 or CNY 9.11, respectively, and willingness-to-pay was hypothesized as CNY 0.6 million in averting one VAPP-induced DALY. IPV-containing schedules are currently cost-ineffective in Shanghai. They may be cost-effective by reducing the prices of IPV, which may accelerate polio eradication in Chinese settings.

Adverse events following immunization with bivalent oral poliovirus vaccine in Jiangsu, China

AIMS

The bivalent oral poliovirus vaccine (bOPV; Sabin types 1 and 3) replaced the trivalent OPV (Sabin types 1, 2 and 3) globally in April 2016. A routine schedule of 1 dose of inactivated poliovirus vaccine and 3 subsequent doses of bOPV was implemented in Jiangsu simultaneously. The schedule was changed to 2 inactivated poliovirus vaccines + 2 bOPV on 1 September 2019. Although OPV type 2 has been removed, challenges persist because of adverse events following immunization (AEFIs) with bOPV. Therefore, we analysed and evaluated the safety profile of bOPV administered in children based on passive postmarketing AEFI surveillance.

METHODS

We collected all bOPV-related AEFI reports in Jiangsu from the Chinese National AEFI Information System (CNAEFIS) between May 2016 and April 2020. We obtained the administered doses of bOPV from the Jiangsu Provincial Electronic Immunization Registries System. A descriptive analysis was performed.

RESULTS

In total, 2084 bOPV-related AEFIs were retrieved from the CNAEFIS. The overall reporting rate was 24.16 per 100 000 doses. Most AEFIs were nonserious. The most frequently reported symptoms were fever, rash and gastrointestinal disorders. Only 1.34% of AEFIs were serious, which thrombocytopenic purpura accounted for the largest category. Seventeen serious adverse events, including 2 vaccine-associated paralytic poliomyelitis (VAPP) cases, were considered to be related to bOPV vaccination. The rate of VAPP was 0.2 per million doses.

CONCLUSION

AEFI analysis showed that bOPV was well tolerated. The events most frequently reported were nonserious. However, bOPV can still cause VAPP. Attention should be given to risks related to bOPV.

Sequential inactivated (IPV) and live oral (OPV) poliovirus vaccines for preventing poliomyelitis

BACKGROUND

Poliomyelitis mainly affects unvaccinated children under five years of age, causing irreversible paralysis or even death. The oral polio vaccine (OPV) contains live attenuated virus, which can, in rare cases, cause a paralysis known as vaccine-associated paralytic polio (VAPP), and also vaccine-derived polioviruses (VDPVs) due to acquired neurovirulence after prolonged duration of replication. The incidence of poliomyelitis caused by wild polio virus (WPV) has declined dramatically since the introduction of OPV and later the inactivated polio vaccine (IPV), however, the cases of paralysis linked to the OPV are currently more frequent than those related to the WPV. Therefore, in 2016, the World Health Organization (WHO) recommended at least one IPV dose preceding routine immunisation with OPV to reduce VAPPs and VDPVs until polio could be eradicated.

OBJECTIVES

To assess the effectiveness, safety, and immunogenicity of sequential IPV-OPV immunisation schemes compared to either OPV or IPV alone.

SEARCH METHODS

In May 2019 we searched CENTRAL, MEDLINE, Embase, 14 other databases, three trials registers and reports of adverse effects on four web sites. We also searched the references of identified studies, relevant reviews and contacted authors to identify additional references.

SELECTION CRITERIA

Randomised controlled trials (RCTs), quasi-RCTs, controlled before-after studies, nationwide uncontrolled before-after studies (UBAs), interrupted time series (ITS) and controlled ITS comparing sequential IPV-OPV schedules (one or more IPV doses followed by one or more OPV doses) with IPV alone, OPV alone or non-sequential IPV-OPV combinations.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 21 studies: 16 RCTs involving 6407 healthy infants (age range 96 to 975 days, mean 382 days), one ITS with 28,330 infants and four nationwide studies (two ITS, two UBA). Ten RCTs were conducted in high-income countries; five in the USA, two in the UK, and one each in Chile, Israel, and Oman. The remaining six RCTs were conducted in middle-income countries; China, Bangladesh, Guatemala, India, and Thailand. We rated all included RCTs at low or unclear risk of bias for randomisation domains, most at high or unclear risk of attrition bias, and half at high or unclear risk for conflict of interests. Almost all RCTs were at low risk for the remaining domains. ITSs and UBAs were mainly considered at low risk of bias for most domains. IPV-OPV versus OPV It is uncertain if an IPV followed by OPV schedule is better than OPV alone at reducing the number of WPV cases (very low-certainty evidence); however, it may reduce VAPP cases by 54% to 100% (three nationwide studies; low-certainty evidence). There is little or no difference in vaccination coverage between IPV-OPV and OPV-only schedules (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.96 to 1.06; 1 ITS study; low-certainty evidence). Similarly, there is little or no difference between the two schedule types for the number of serious adverse events (SAEs) (RR 0.88, 95% CI 0.46 to 1.70; 4 studies, 1948 participants; low-certainty evidence); or the number of people with protective humoral response P1 (moderate-certainty evidence), P2 (for the most studied schedule; two IPV doses followed by OPV; low-certainty evidence), and P3 (low-certainty evidence). Two IPV doses followed by bivalent OPV (IIbO) may reduce P2 neutralising antibodies compared to trivalent OPV (moderate-certainty evidence), but may make little or no difference to P1 or P2 neutralising antibodies following an IIO schedule or OPV alone (low-certainty evidence). Both IIO and IIbO schedules may increase P3 neutralising antibodies compared to OPV (moderate-certainty evidence). It may also lead to lower mucosal immunity given increased faecal excretion of P1 (low-certainty evidence), P2 and P3 (moderate-certainty evidence) after OPV challenge. IPV-OPV versus IPV It is uncertain if IPV-OPV is more effective than IPV alone at reducing the number of WPV cases (very low-certainty evidence). There were no data regarding VAPP cases. There is no clear evidence of a difference between IPV-OPV and OPV schedules for the number of people with protective humoral response (low- and moderate-certainty evidence). IPV-OPV schedules may increase mean titres of P1 neutralising antibodies compared to OPV alone (low- and moderate-certainty evidence), but the effect on P2 and P3 titres is not clear (very low- and moderate-certainty evidence). IPV-OPV probably reduces the number of people with P3 poliovirus faecal excretion after OPV challenge with IIO and IIOO sequences (moderate-certainty evidence), and may reduce the number with P2 (low-certainty evidence), but not with P1 (very low-certainty evidence). There may be little or no difference between the schedules in number of SAEs (RR 0.92, 95% CI 0.60 to 1.43; 2 studies, 1063 participants, low-certainty evidence). The number of persons with P2 protective humoral immunity and P2 neutralising antibodies are probably lower with most sequential schemes without P2 components (i.e. bOPV) than with trivalent OPV or IVP alone (moderate-certainty evidence). IPV (3)-OPV versus IPV (2)-OPV One study (137 participants) showed no clear evidence of a difference between three IPV doses followed by OPV and two IPV doses followed by OPV, on the number of people with P1 (RR 0.98, 95% CI 0.93 to 1.03), P2 (RR 1.00, 95% CI 0.97 to 1.03), or P3 (RR 1.01, 95% CI 0.97 to 1.05) protective humoral and intestinal immunity; all moderate-certainty evidence. This study did not report on any other outcomes.

AUTHORS' CONCLUSIONS

IPV-OPV compared to OPV may reduce VAPPs without affecting vaccination coverage, safety or humoral response, except P2 with sequential schemes without P2 components, but increase poliovirus faecal excretion after OPV challenge for some polio serotypes. Compared to IPV-only schedules, IPV-OPV may have little or no difference on SAEs, probably has little or no effect on persons with protective humoral response, may increase neutralising antibodies, and probably reduces faecal excretion after OPV challenge of certain polio serotypes. Using three IPV doses as part of a IPV-OPV schedule does not appear to be better than two IPV doses for protective humoral response. Sequential schedules during the transition from OPV to IPV-only immunisation schedules seems a reasonable option aligned with current WHO recommendations. Findings could help decision-makers to optimise polio vaccination policies, reducing inequities between countries.

Vaccine-associated paralytic poliomyelitis in the Russian Federation in 1998-2014

OBJECTIVES

Different polio vaccination schemes have been used in Russia: oral polio vaccine (OPV) was used in 1998-2007 and inactivated polio vaccine (IPV) followed by OPV in 2008-2014. This article presents the characteristics of vaccine-associated paralytic poliomyelitis (VAPP) cases in Russia during this period.

METHODS

VAPP cases were identified through the acute flaccid paralysis surveillance system, classified by the National Expert Classification Committee. Criteria for a 'recipient VAPP' (rVAPP) case were poliomyelitis symptoms 6-30days after OPV administration, isolation of the vaccine virus, and residual paralysis 60days after disease onset. Unvaccinated cases with a similar picture 6-60days after contact with an OPV recipient were classified as 'contact VAPP' (cVAPP) cases.

RESULTS

During 1998-2014, 127 VAPP cases were registered: 82 rVAPP and 45 cVAPP. During the period in which only OPV was used, rVAPP cases prevailed (73.8%); cases of rVAPP were reduced during the sequential scheme period (15%). Poliovirus type 3 (39.5%) and type 2 (23.7%) were isolated more often. Vaccine-derived poliovirus types 1, 2, and 3 were isolated from three cases of cVAPP. The incidence of VAPP cases was higher during the period of OPV use (1 case/1.59 million OPV doses) than during the sequential scheme period (1 case/4.18 million doses).

CONCLUSION

The risk of VAPP exists if OPV remains in the vaccination schedule.

Questions regarding the safety and duration of immunity following live yellow fever vaccination

INTRODUCTION

The World Health Organization (WHO) and other health agencies have concluded that yellow fever booster vaccination is unnecessary since a single dose of vaccine confers lifelong immunity. Areas covered: We reviewed the clinical studies cited by health authorities in their investigation of both the safety profile and duration of immunity for the YFV-17D vaccine and examined the position that booster vaccination is no longer needed. We found that antiviral immunity may be lost in 1-in-3 to 1-in-5 individuals within 5 to 10 years after a single vaccination and that children may be at greater risk for primary vaccine failure. The safety profile of YFV-17D was compared to other licensed vaccines including oral polio vaccine (OPV) and the rotavirus vaccine, RotaShield, which have subsequently been withdrawn from the US and world market, respectively. Expert commentary: Based on these results and recent epidemiological data on vaccine failures (particularly evident at >10 years after vaccination), we believe that current recommendations to no longer administer YFV-17D booster vaccination be carefully re-evaluated, and that further development of safer vaccine approaches should be considered.

Preparation for global introduction of inactivated poliovirus vaccine: safety evidence from the US Vaccine Adverse Event Reporting System, 2000-12

BACKGROUND

Safety data from countries with experience in the use of inactivated poliovirus vaccine (IPV) are important for the global polio eradication strategy to introduce IPV into the immunisation schedules of all countries. In the USA, IPV has been included in the routine immunisation schedule since 1997. We aimed to analyse adverse events after IPV administration reported to the US Vaccine Adverse Event Reporting System (VAERS).

METHODS

We analysed all VAERS data associated with IPV submitted between Jan 1, 2000, and Dec 31, 2012, either as individual or as combination vaccines, for all age and sex groups. We analysed the number and event type (non-serious, non-fatal serious, and death reports) of individual reports, and explored the most commonly coded event terms to describe the adverse event. We classified death reports according to previously published body-system categories (respiratory, cardiovascular, neurological, gastrointestinal, other infectious, and other non-infectious) and reviewed death reports to identify the cause of death. We classified sudden infant death syndrome as a separate cause of death considering previous concerns about sudden infant syndrome after vaccines. We used empirical Bayesian data mining methods to identify disproportionate reporting of adverse events for IPV compared with other vaccines. Additional VAERS data from 1991 to 2000 were analysed to compare the safety profiles of IPV and oral poliovirus vaccine (OPV).

FINDINGS

Of the 41,792 adverse event reports submitted, 39,568 (95%) were for children younger than 7 years. 38,381 of the reports for children in this age group (97%) were for simultaneous vaccination with IPV and other vaccines (most commonly pneumococcal and acellular pertussis vaccines), whereas standalone IPV vaccines accounted for 0·5% of all reports. 34,880 reports were for non-serious events (88%), 3905 reports were for non-fatal serious events (10%), and 783 reports were death reports (2%). Injection-site erythema was the most commonly coded term for non-serious events (29%), and pyrexia for non-fatal serious events (38%). Most deaths (96%) were in children aged 12 months or younger; most (52%) had sudden infant death syndrome as the reported cause of death. The safely profiles of combined IPV and whole-cell pertussis vaccines, OPV and whole-cell pertussis vaccines, and OPV and acellular pertussis vaccines were similar. We noted no indication of disproportionate reporting of adverse events after immunisation with IPV-containing vaccines compared with other vaccines between 1990 and 2013.

INTERPRETATION

Fairly few adverse events were reported for the more than 250 million IPV doses distributed between 2000 and 2012. Sudden infant death syndrome reports after IPV were consistent with reporting patterns for other vaccines. No new or unexpected vaccine safety problems were identified for fatal, non-fatal serious, and non-serious reports in this assessment of adverse events after IPV.

FUNDING

None.

Pharmacovigilance in children: detecting adverse drug reactions in routine electronic healthcare records. A systematic review

AIMS

A systematic review of the literature published in English over 10 years was undertaken in order to describe the use of electronic healthcare data in the identification of potential adverse drug reactions (ADRs) in children.

METHODS

MEDLINE and EMBASE were searched using MESH headings and text words. Titles, keywords and abstracts were checked for age <18 years, potential ADRs and electronic healthcare data. Information extracted included age, data source, pharmacovigilance method, medicines and ADRs. Studies were quality assessed.

RESULTS

From 14 804 titles, 314 had a full text review and 71 were included in the final review. Fifty were published in North America, 10 in Scandinavia. Study size ranged from less than 1000 children to more than 10 million. Sixty per cent of studies used data from one source. Comparative observational studies were most commonly reported (66.2%) with 15% using passive surveillance. Electronic healthcare data set linkage and the quality of the data source were poorly reported. ADRs were classified using the International Classification of Disease (ICD10). Multi-system reactions were most commonly studied, followed by central nervous system and mental and behavioural disorders. Vaccines were most frequently prescribed followed by corticosteroids, general anaesthetics and antidepressants.

CONCLUSIONS

Routine electronic healthcare records were increasingly reported to be used for pharmacovigilance in children. This growing and important health protection activity could be enhanced by consistent reporting of studies to improve the identification, interpretation and generalizability of the evidence base.

Enteroviruses, hygiene and type 1 diabetes: toward a preventive vaccine

Enteroviruses and humans have long co-existed. Although recognized in ancient times, poliomyelitis and type 1 diabetes (T1D) were exceptionally rare and not epidemic, due in large part to poor sanitation and personal hygiene which resulted in repeated exposure to fecal-oral transmitted viruses and other infectious agents and viruses and the generation of a broad protective immunity. As a function of a growing acceptance of the benefits of hygienic practices and microbiologically clean(er) water supplies, the likelihood of exposure to diverse infectious agents and viruses declined. The effort to vaccinate against poliomyelitis demonstrated that enteroviral diseases are preventable by vaccination and led to understanding how to successfully attenuate enteroviruses. Type 1 diabetes onset has been convincingly linked to infection by numerous enteroviruses including the group B coxsackieviruses (CVB), while studies of CVB infections in NOD mice have demonstrated not only a clear link between disease onset but an ability to reduce the incidence of T1D as well: CVB infections can suppress naturally occurring autoimmune T1D. We propose here that if we can harness and develop the capacity to use attenuated enteroviral strains to induce regulatory T cell populations in the host through vaccination, then a vaccine could be considered that should function to protect against both autoimmune as well as virus-triggered T1D. Such a vaccine would not only specifically protect from certain enterovirus types but more importantly, also reset the organism's regulatory rheostat making the further development of pathogenic autoimmunity less likely.

Vaccine-associated paralytic poliomyelitis: a review of the epidemiology and estimation of the global burden

BACKGROUND

Vaccine-associated paralytic poliomyelitis (VAPP) is a rare adverse event associated with oral poliovirus vaccine (OPV). This review summarizes the epidemiology and provides a global burden estimate.

METHODS

A literature review was conducted to abstract the epidemiology and calculate the risk of VAPP. A bootstrap method was applied to calculate global VAPP burden estimates.

RESULTS

Trends in VAPP epidemiology varied by country income level. In the low-income country, the majority of cases occurred in individuals who had received >3 doses of OPV (63%), whereas in middle and high-income countries, most cases occurred in recipients after their first OPV dose or unvaccinated contacts (81%). Using all risk estimates, VAPP risk was 4.7 cases per million births (range, 2.4-9.7), leading to a global annual burden estimate of 498 cases (range, 255-1018). If the analysis is limited to estimates from countries that currently use OPV, the VAPP risk is 3.8 cases per million births (range, 2.9-4.7) and a burden of 399 cases (range, 306-490).

CONCLUSIONS

Because many high-income countries have replaced OPV with inactivated poliovirus vaccine, the VAPP burden is concentrated in lower-income countries. The planned universal introduction of inactivated poliovirus vaccine is likely to substantially decrease the global VAPP burden by 80%-90%.

Deficiency of immunity to poliovirus type 3: a lurking danger?

Background

Europe was certified to be polio-free in 2002 by the WHO. However, wild polioviruses remain endemic in India, Pakistan, Afghanistan, and Nigeria, occasionally causing polio outbreaks, as in Tajikistan in 2010. Therefore, effective surveillance measures and vaccination campaigns remain important. To determine the poliovirus immune status of a German study population, we retrospectively evaluated the seroprevalence of neutralizing antibodies (NA) to the poliovirus types 1, 2 and 3 (PV1, 2, 3) in serum samples collected from 1,632 patients admitted the University Hospital of Frankfurt am Main, Germany, in 2001, 2005 and 2010.

Methods

Testing was done by using a standardized microneutralization assay.

Results

Level of immunity to PV1 ranged between 84.2% (95%CI: 80.3-87.5), 90.4% (88.3-92.3) and 87.5% (85.4-88.8) in 2001, 2005 and 2010. For PV2, we found 90.8% (87.5-90.6), 91.3% (89.3-93.1) and 89.8% (88.7-90.9), in the same period. Seroprevalence to PV3 was 76.6% (72.2-80.6), 69.8% (66.6-72.8) and 72.9% (67.8-77.5) in 2001 and 2005 and 2010, respectively. In 2005 and 2010 significant lower levels of immunity to PV3 in comparison to PV1 and 2 were observed. Since 2001, immunity to PV3 is gradually, but not significantly decreasing.

Conclusion

Immunity to PV3 is insufficient in our cohort. Due to increasing globalization and worldwide tourism, the danger of polio-outbreaks is not averted - even not in developed countries, such as Germany. Therefore, vaccination remains necessary.

A live-attenuated HSV-2 ICP0 virus elicits 10 to 100 times greater protection against genital herpes than a glycoprotein D subunit vaccine

Glycoprotein D (gD-2) is the entry receptor of herpes simplex virus 2 (HSV-2), and is the immunogen in the pharmaceutical industry's lead HSV-2 vaccine candidate. Efforts to prevent genital herpes using gD-2 subunit vaccines have been ongoing for 20 years at a cost in excess of $100 million. To date, gD-2 vaccines have yielded equivocal protection in clinical trials. Therefore, using a small animal model, we sought to determine if a live-attenuated HSV-2 ICP0⁻ virus would elicit better protection against genital herpes than a gD-2 subunit vaccine. Mice immunized with gD-2 and a potent adjuvant (alum+monophosphoryl lipid A) produced high titers of gD-2 antibody. While gD-2-immunized mice possessed significant resistance to HSV-2, only 3 of 45 gD-2-immunized mice survived an overwhelming challenge of the vagina or eyes with wild-type HSV-2 (MS strain). In contrast, 114 of 115 mice immunized with a live HSV-2 ICP0⁻ virus, 0ΔNLS, survived the same HSV-2 MS challenges. Likewise, 0ΔNLS-immunized mice shed an average 125-fold less HSV-2 MS challenge virus per vagina relative to gD-2-immunized mice. In vivo imaging demonstrated that a luciferase-expressing HSV-2 challenge virus failed to establish a detectable infection in 0ΔNLS-immunized mice, whereas the same virus readily infected naïve and gD-2-immunized mice. Collectively, these results suggest that a HSV-2 vaccine might be more likely to prevent genital herpes if it contained a live-attenuated HSV-2 virus rather than a single HSV-2 protein.

Investigations of clinical isolations of oral poliovirus vaccine strains between 2000 and 2005 in southern Taiwan

BACKGROUND

In Taiwan, trivalent oral poliovirus vaccine (tOPV) is in the routine immunization schedule, but its association with illnesses had not been examined.

OBJECTIVES

To investigate clinical presentations and viral characteristics of patients with poliovirus isolates.

STUDY DESIGN

Clinical data, vaccination records and viral sequences were retrospectively analyzed for patients from whom polioviruses were isolated during 2000-2005.

RESULTS

OPV-like strains were the only pathogen identified in 208 children who were diagnosed with lower respiratory tract infection (24.5%), acute gastroenteritis (16.8%) or upper respiratory tract infection (10.6%). Timing of poliovirus isolation relative to the tOPV vaccination was unusual in 59 patients, including 6 before any dose and 53 more than 10 weeks after the 3rd or later dose of tOPV. Sequence analyses of the VP1, 2C and 3C/D regions for 19 poliovirus isolates revealed that 4 had previously reported neurovirulence reversions, 1 had intertypic recombination, and 6 had both. No patient had neurological complications, but 3 died of myocarditis, including 2 with recombinant strains and 1 who never received OPV.

CONCLUSION

This study describes the isolation of OPV-like strains from patients with a variety of illnesses, raising concerns about their pathogenic potential in an area where tOPV is routinely administered. The detection of genetic variations among OPV-like strains warrants continuing surveillance for these variants in patients with severe illnesses besides neurological complications.

Direct extraction of Sabin poliovirus genomes from human fecal samples using a guanidine thiocyanate extraction method

To permit rapid and efficient detection of Sabin poliovirus type 3 from human fecal samples, we developed a guanidine thiocyanate (GuSCN) extraction and reverse transcriptase polymerase chain reaction (RT-PCR) method. Using 10-fold serial dilutions from stock Sabin-Leon 12 a1b poliovirus type 3 at 10(7) TCID(50) per 0.1 ml, genome was detected to a dilution of 10(3) TCID(50) per 0.1 ml. A total of 40 archived fecal samples were examined using this GuSCN extraction method followed by RT-PCR. Fourteen of 20 poliovirus type 3 tissue culture-positive specimens (70%) and two of 20 tissue culture-negative specimens (10%) were detected by GuSCN extraction and RT-PCR. All positive and negative extraction and RT-PCR controls were identified accurately. This GuSCN extraction and RT-PCR technique is rapid, inexpensive, and can be readily adapted to identify genome sequences of other enterovirus types in large numbers of fecal samples. Moreover, the GuSCN technique extracts viral RNA directly from fecal samples, allowing observation of in vivo alterations of genome sequences. Further studies are underway to examine the development of revertant point mutations in the Sabin poliovirus type 3 genome following oral administration of trivalent Sabin Oral Poliovirus Vaccine to humans.

Characterization of a Vero cell-adapted virulent strain of enterovirus 71 suitable for use as a vaccine candidate

Enterovirus 71 (EV71) is a neurotrophic virus that causes seasonal morbidity and mortality in children throughout the world with increasing frequency in recent years. Because of the lack of an effective antiviral agent, primary prevention, including the development of effective vaccines, is a top priority in terms of control strategies. Poliovirus vaccine technology, both live attenuated and inactivated, killed virus vaccines, can be adopted for use with EV71 because of their relatedness. In this study, we have characterized a laboratory-adapted EV71 strain, YN3-4a, which exhibits different characteristics from those of its parent isolate, neu, in having a rapid growth rate in Vero cells, a larger plaque size, and a lower LD(50) in newborn mice. The YN3-4a can be produced at a high viral titer of up to 10(10) tissue culture infective dose (TCID(50)) when grown in Vero cells, an approved substrate for virus vaccine production. Mouse antiserum raised against YN3-4a can neutralize a broad range of strains of EV71 isolated at different times from a variety of geographic regions. On passage in Vero cells, YN3-4a remained genetically and phenotypically stable. Many of the above-described features, such as high viral yield, strong immunogenicity, broad-based antigenic coverage, and passage stability, are desirable features in a prototype virus for the development of an inactivated viral vaccine.