Immunogenicity of Different Routine Poliovirus Vaccination Schedules: A Randomized, Controlled Trial in Karachi, Pakistan

Evaluation of the immunization effectiveness of bOPV booster immunization and IPV revaccination

To provide a basis for further optimization of the polio sequential immunization schedule, this study evaluated the effectiveness of booster immunization with one dose of bivalent oral poliovirus vaccine (bOPV) at 48 months of age after different primary polio immunization schedules. At 48 months of age, one dose of bOPV was administered, and their poliovirus types 1-3 (PV1, PV2, and PV3, respectively)-specific neutralizing antibody levels were determined. Participants found to be negative for any type of PV-specific neutralizing antibody at 24, 36, or 48 months of age were re-vaccinated with inactivated polio vaccine (IPV). The 439 subjects who received a bOPV booster immunization at the age of 48 months had lower PV2-specific antibody levels compared with those who received IPV. One dose of IPV during basic polio immunization induced the lowest PV2-specific antibody levels. On the basis of our findings, to ensure that no less than 70% of the vaccinated have protection efficiency, we recommend the following: if basic immunization was conducted with 1IPV + 2bOPV (especially Sabin strain-based IPV), a booster immunization with IPV is recommended at 36 months of age, whereas if basic immunization was conducted with 2IPV + 1bOPV, a booster immunization with IPV is recommended at 48 months of age. A sequential immunization schedule of 2IPV + 1bOPV + 1IPV can not only maintain high levels of antibody against PV1 and PV3 but also increases immunity to PV2 and induces early intestinal mucosal immunity, with relatively good safety. Thus, this may be the best sequential immunization schedule for polio in countries or regions at high risk for polio.

Assessment of serological responses following vaccination campaigns with type 2 novel oral polio vaccine: a population-based study in Tajikistan in 2021

BACKGROUND

Novel oral poliovirus vaccine type 2 (nOPV2) was used to control an outbreak of type 2 circulating vaccine derived poliovirus (cVDPV2) in Tajikistan, in 2021. We measured seroconversion and seroprevalence of type 2 polio antibodies in children who were reported to have received two doses of nOPV2 in outbreak response campaigns.

METHODS

In this community serosurvey, children born after Jan 1, 2016 were enrolled from seven districts in Tajikistan. Dried blood spot cards were collected before nOPV2 campaigns and after the first and second rounds of the campaigns and were sent to the Centers for Disease Control and Prevention (Atlanta, GA, USA) for microneutralisation assay to determine presence of polio antibodies. The primary endpoint was to assess change in seroprevalence and seroconversion against poliovirus serotype 2 after one and two doses of nOPV2.

FINDINGS

228 (97%) of 236 enrolled children were included in the analysis. The type 2 antibody seroprevalence was 26% (53/204; 95% CI 20 to 33) before nOPV2, 77% (161/210; 70 to 82) after one dose of nOPV2, and 83% (174/209; 77 to 88) after two doses of nOPV2. The increase in seroprevalence was statistically significant between baseline and after one nOPV2 dose (51 percentage points [42 to 59], p<0·0001), but not between the first and second doses (6 percentage points [-2 to 15], p=0·12). Seroconversion from the first nOPV2 dose, 67% (89/132; 59 to 75), was significantly greater than that from the second nOPV2 dose, 44% (20/45; 30 to 60; χ² p=0·010). Total seroconversion after two nOPV2 doses was 77% (101/132; 68 to 83).

INTERPRETATION

Our study demonstrated strong immune responses following nOPV2 outbreak response campaigns in Tajikistan. Our results support previous clinical trial data on the generation of poliovirus type 2 immunity by nOPV2 and provide evidence that nOPV2 can be appropriate for the cVDPV2 outbreak response. The licensure and WHO prequalification of nOPV2 should be accelerated to facilitate wider use of the vaccine.

FUNDING

World Health Organization, Centers for Disease Control and Prevention, and Rotary International.

One Full or Two Fractional Doses of Inactivated Poliovirus Vaccine for Catch-up Vaccination in Older Infants: A Randomized Clinical Trial in Bangladesh

BACKGROUND

The polio eradication endgame called for the removal of trivalent oral poliovirus vaccine (OPV) and introduction of bivalent (types 1 and 3) OPV and inactivated poliovirus vaccine (IPV). However, supply shortages have delayed IPV administration to tens of millions of infants, and immunogenicity data are currently lacking to guide catch-up vaccination policies.

METHODS

We conducted an open-label randomized clinical trial assessing 2 interventions, full or fractional-dose IPV (fIPV, one-fifth of IPV), administered at age 9-13 months with a second dose given 2 months later. Serum was collected at days 0, 60, 67, and 90 to assess seroconversion, priming, and antibody titer. None received IPV or poliovirus type 2-containing vaccines before enrolment.

RESULTS

A single fIPV dose at age 9-13 months yielded 75% (95% confidence interval [CI], 6%-82%) seroconversion against type 2, whereas 2 fIPV doses resulted in 100% seroconversion compared with 94% (95% CI, 89%-97%) after a single full dose (P < .001). Two doses of IPV resulted in 100% seroconversion.

CONCLUSIONS

Our study confirmed increased IPV immunogenicity when administered at an older age, likely due to reduced interference from maternally derived antibodies. Either 1 full dose of IPV or 2 doses of fIPV could be used to vaccinate missed cohorts, 2 fIPV doses being antigen sparing and more immunogenic.

CLINICAL TRIAL REGISTRATION

NCT03890497.

Review of use of inactivated poliovirus vaccine in campaigns to control type 2 circulating vaccine derived poliovirus (cVDPV) outbreaks

Delivering inactivated poliovirus vaccine (IPV) with oral poliovirus vaccine (OPV) in campaigns has been explored to accelerate the control of type 2 circulating vaccine-derived poliovirus (cVDPV) outbreaks. A review of scientific literature suggests that among populations with high prevalence of OPV failure, a booster with IPV after at least two doses of OPV may close remaining humoral and mucosal immunity gaps more effectively than an additional dose of trivalent OPV. However, IPV alone demonstrates minimal advantage on humoral immunity compared with monovalent and bivalent OPV, and cannot provide the intestinal immunity that prevents infection and spread to those individuals not previously exposed to live poliovirus of the same serotype (i.e. type 2 for children born after the switch from trivalent to bivalent OPV in April 2016). A review of operational data from polio campaigns shows that addition of IPV increases the cost and logistic complexity of campaigns. As a result, campaigns in response to an outbreak often target small areas. Large campaigns require a delay to ensure logistics are in place for IPV delivery, and may need implementation in phases that last several weeks. Challenges to delivery of injectable vaccines through house-to-house visits also increases the risk of missing the children who are more likely to benefit from IPV: those with difficult access to routine immunization and other health services. Based upon this information, the Strategic Advisory Group of Experts in immunization (SAGE) recommended in October 2020 the following strategies: provision of a second dose of IPV in routine immunization to reduce the risk and number of paralytic cases in countries at risk of importation or new emergences; and use of type 2 OPV in high-quality campaigns to interrupt transmission and avoid seeding new type 2 cVDPV outbreaks.

Immunogenicity of Fractional Dose Inactivated Poliovirus Vaccine in India

INTRODUCTION

Following the withdrawal of Sabin type 2 from trivalent oral poliovirus vaccine (tOPV) in 2016, the introduction of ≥1 dose of inactivated poliovirus vaccine (IPV) in routine immunization was recommended, either as 1 full dose (0.5mL, intramuscular) or 2 fractional doses of IPV (fIPV-0.1mL, intradermal). India opted for fIPV. We conducted a comparative assessment of IPV and fIPV.

METHODS

This was a 4-arm, open-label, multicenter, randomized controlled trial. Infants were enrolled and vaccines administered according to the study design, and the blood was drawn at age 6, 14, and 18 weeks for neutralization testing against all 3 poliovirus types.

RESULTS

Study enrolled 799 infants. The seroconversion against type 2 poliovirus with 2 fIPV doses was 85.8% (95% confidence interval [CI]: 80.1%-90.0%) when administered at age 6 and 14 weeks, 77.0% (95% CI: 70.5-82.5) when given at age 10 and 14 weeks, compared to 67.9% (95% CI: 60.4-74.6) following 1 full-dose IPV at age 14 weeks.

CONCLUSION

The study demonstrated the superiority of 2 fIPV doses over 1 full-dose IPV in India. Doses of fIPV given at 6 and 14 weeks were more immunogenic than those given at 10 and 14 weeks. Clinical Trial Registry of India (CTRI). Clinical trial registration number was CTRI/2017/02/007793.

Immunogenicity of sequential poliovirus vaccination schedules with different strains of poliomyelitis vaccines in Chongqing, China: a cross-sectional survey

A new vaccination schedule with one dose of inactivated polio vaccine (IPV) followed by three doses of bivalent oral attenuated live polio vaccine (bOPV) was introduced in China in 2016. Both Sabin IPV (sIPV) and Salk IPV (wIPV) sequentially with bOPV were accepted in the Chinese routine vaccination schedule. We intended to assess the immunogenicity of the current primary schedule (s/wIPV-bOPV-bOPV) and the schedule in the early stage of the switch (tOPV-bOPV-bOPV), and compare immunogenicity between the groups with different polio virus strains. Healthy infants aged 60–89 days were recruited in hospitals in Chongqing. Infants were assigned to one of three treatments (tOPV-bOPV-bOPV, sIPV-bOPV-bOPV or wIPV-bOPV-bOPV) by enrollment time. Polio neutralizing antibody (NA) assays were conducted to assess immunity. 1027 eligible infants were enrolled. Over 95% seroprotection rates against type I poliovirus (PV1) and type III poliovirus (PV3) were observed in all groups. Infants who received tOPV-bOPV-bOPV had higher antibody titers against type II poliovirus (PV2) than did the IPV-bOPV-bOPV. The geometric mean titers (GMTs) of PV2 were only ~20 in the IPV-bOPV-bOPV. GMTs of PV1 were higher than PV3 in s/wIPV-bOPV-bOPV. The primary schedule of s/wIPV-bOPV-bOPV is insufficient to protect children against PV2, and the NA titer to PV3 is lower. Higher antibody responses were induced in sIPV-bOPV-bOPV than that in wIPV-bOPV-bOPV. Supplementary vaccination with one dose of IPV is necessary for children who had no tOPV immune history or had only one IPV to induce higher levels of immunity against PV2 and PV3.

Implication of a High Risk for Type 2 Vaccine-Derived Poliovirus Emergence and Transmission After the Switch From Trivalent to Bivalent Oral Poliovirus Vaccine

BACKGROUND

China implemented the globally synchronized switch from trivalent oral poliovirus vaccine (tOPV) to bivalent OPV (bOPV) and introduced 1 dose of inactivated poliovirus vaccine on 1 May 2016. We assessed the impact of the switch on the immunity level against poliovirus, especially type 2.

METHODS

Children born between 2014 and 2017, who were brought to the hospitals in Urumqi city, Xinjiang Province in 2017, were enrolled and blood samples were collected to test for antibody titers against poliovirus. A comparison of seroprevalence between the children born before (preswitch group) and after the switch (postswitch group) was performed to assess the impact of the switch on the immunity level against polio.

RESULTS

A total of 172 subjects were enrolled. The overall seroprevalences were 98.8%, 79.1%, and 98.3% for types 1, 2, and 3, respectively. Seroprevalence for type 2 significantly decreased from 91.6% in the preswitch group to 67.4% in the postswitch group, but no statistically significant change was observed for both types 1 and 3.

CONCLUSIONS

The switch from tOPV to bOPV can provide high-level immunity against types 1 and 3 but not against type 2, indicating a high risk of type 2 vaccine-derived poliovirus emergence and transmission.

Stool Serology: Development of a Non-Invasive Immunological Method for the Detection of Enterovirus-Specific Antibodies in Congo Gorilla Faeces

Background: The incidence of poliovirus has been significantly reduced by as much as 99.9% globally. Alongside this, however, vaccine-associated paralytic poliomyelitis has emerged. Previously, our team reported in the Lésio-Louna-Léfini Nature Reserve (Republic of Congo) the presence of a new Enterovirus C (Ibou002) in a male gorilla that was put away because of clinical symptoms of facial paralysis. This new virus, isolated was from the stool samples of this gorilla but also from the excrement of an eco-guardian, is very similar to Coxsackievirus (EV-C99) as well as poliovirus 1 and 2. We hypothesised that these symptoms might be due to poliovirus infection. To test our hypothesis, we developed and optimised a non-invasive immunoassay for the detection of Enterovirus-specific antibodies in gorilla faeces that could be useful for routine serosurveillance in such cases. Methods: In order to assess the potential role of poliovirus infection, we have developed and optimised a protocol, based on the lyophilisation and solubilisation of small volumes of stool extracts from 16 gorilla and 3 humans, to detect specific antibodies by western blot and ELISA. Results: First, total immunoglobulins were detected in the concentrated stool extracts. Specific antibodies were then detected in 4/16 gorilla samples and 2/3 human samples by western blot using both the polio vaccine antigen and the Ibou002 antigen and by ELISA using the polio vaccine antigen. Humoral responses were greater with the Ibou002 antigen. Conclusion: We therefore suggest that this recombinant virus could lead to a polio-like disease in the endangered western lowland gorilla. The development of a non-invasive approach to detect microorganism-specific immunoglobulins from faecal samples opens numerous prospects for application in zoonotic infectious diseases and could revolutionise the screening of animals for important emerging infections, such as Ebola fever, rabies and coronavirus infections.

Randomized Controlled Clinical Trial of bivalent Oral Poliovirus Vaccine and Inactivated Poliovirus Vaccine in Nigerian Children

BACKGROUND

We conducted a trial in Nigeria to assess the immunogenicity of the new bOPV + IPV immunization schedule and gains in type 2 immunity with addition of second dose of IPV. The trial was conducted in August 2016-March 2017 period, well past the tOPV-bOPV switch in April 2016.

METHODS

This was an open-label, two-arm, non-inferiority, multi-center, randomized controlled trial. We enrolled 572 infants of age ≤14 days and randomized them into two arms. Arm A received bOPV at birth, 6 and 10 weeks, bOPV+IPV at week 14 and IPV at week 18. Arm B received IPV each at 6, 10, 14 weeks and bOPV at 18 weeks of age.

RESULTS

Seroconversion rates for poliovirus types 1 and 3, respectively, were 98.9% (95%CI:96.7-99.8) and 98.1% (95%CI:88.2-94.8) in Arm A, and 89.6% (95%CI:85.4-93.0) and 98.5% (95%CI:96.3-99.6) in Arm B. Type 2 seroconversion with one dose IPV in Arm A was 72.0% (95%CI:66.2-77.3), which increased significantly with addition of second dose to 95.9% (95%CI:92.8-97.9).

CONCLUSION

This first trial on the new EPI schedule in a sub-Saharan African country demonstrated excellent immunogenicity against poliovirus types 1 and 3, and substantial/enhanced immunogenicity against poliovirus type 2 after 1 to 2 doses of IPV respectively.

Immunogenicity and safety of different sequential schedules of Sabin strain-based inactivated poliovirus vaccination: A randomized, controlled, open-label, phase IV clinical trial in China

BACKGROUND

The immunogenicity and safety of the sequential schedule of Sabin strain-based inactivated poliovirus vaccine (sIPV) and bivalent oral poliovirus vaccine (bOPV) remains poorly understood in Chinese population.

METHODS

A multi-center, open-label, randomized controlled trial was performed involving 648 healthy infants aged 2 months from Inner Mongolia, Shanxi, and Hebei provinces. These participants were divided into three groups: sIPV-bOPV-bOPV, sIPV-sIPV-bOPV, and sIPV-sIPV-sIPV. Doses were administered sequentially at age 2, 3, and 4 months. Neutralisation assays were tested using sera collected at 2 months and 5 months.

RESULTS

A total of 569 were included in the per-protocol analysis. The seroconversion rates of poliovirus type 1 and 3 were 100% in all three groups, the seroconversion rate of poliovirus type 2 was 91.53% (173/189) (95% CI: 86.62-95.08) in the sIPV-bOPV-bOPV group, 98.38% (182/185) (95% CI: 95.33-99.66) in the sIPV-sIPV-bOPV group, and 99.49% (194/195) (95% CI: 97.18-99.99) in the sIPV-sIPV-sIPV group. For the seroconversion rate of poliovirus types 1 and 3, the sIPV-bOPV-bOPV and sIPV-sIPV-bOPV groups were non-inferior to the sIPV-sIPV-sIPV group. For the seroconversion rate of poliovirus type 2, the sIPV-sIPV-bOPV group was non-inferior to the sIPV-sIPV-sIPV group, and the sIPV-bOPV-bOPV group was inferior to the sIPV-sIPV-sIPV group. All three groups exhibited good safety, with two serious adverse events reported, that were unrelated to vaccine.

CONCLUSIONS

In china, a new vaccination schedule that including 2 doses of IPV in the national immunization programs is essential. Trial registration ClinicalTrials.govNCT04054492.

The Gut of Healthy Infants in the Community as a Reservoir of ESBL and Carbapenemase-Producing Bacteria

The recent rapid rise of multi-drug resistant Enterobacteriaceae (MDR-E) is threatening the treatment of common infectious diseases. Infections with such strains lead to increased mortality and morbidity. Using a cross-sectional study, we aimed to estimate the prevalence of gut colonization with extended spectrum beta-lactamase (ESBL) producing Enterobacteriaceae among healthy infants born in Pakistan, a setting with high incidence of MDR-E infections. Stool samples were collected from 104 healthy infants between the ages of 5 and 7 months. Enterobacteriaceae isolates were screened for resistance against several antimicrobial classes. Presence of ESBL and carbapenemase genes was determined using multiplex PCR. Sequence types were assigned to individual strains by multi-locus sequence typing. Phylogenetic analysis of Escherichia coli was done using the triplex PCR method. Forty-three percent of the infants were positive for ESBL-producing Enterobacteriaceae, the majority of which were E. coli. We identified several different ESBL E. coli sequence types most of which belonged to the phylogenetic group B2 (23%) or D (73%). The widespread colonization of infants in a developing country with ESBL-producing Enterobacteriaceae is concerning. The multiple sequence types and reported non-human sources support that multiple non-epidemic MDR lineages are circulating in Pakistan with healthy infants as a common reservoir.

Immunogenicity of three sequential schedules with Sabin inactivated poliovirus vaccine and bivalent oral poliovirus vaccine in Zhejiang, China: an open-label, randomised, controlled trial

BACKGROUND

The globally synchronised introduction of inactivated poliovirus vaccine (IPV) and replacement of trivalent oral poliovirus vaccine (OPV) with bivalent OPV (bOPV) were successfully implemented in China's routine immunisation programme in May, 2016. In response to the global shortage of Salk-strain IPV, Sabin-strain IPV production was encouraged to develop and use in low-income and middle-income countries. We assessed the immunogenicity of the current routine poliovirus vaccination schedule in China and compared it with alternative schedules that use Sabin-strain IPV (sIPV) and bOPV.

METHODS

This open-label, randomised, controlled trial recruited healthy infants aged 60-75 days from two centres in Zhejiang, China. Eligible infants were full-term, due for their first polio vaccination, weighed more than 2·5 kg at birth, were healthy on physical examination with no obvious medical conditions, and had no contraindications to vaccination. Infants were randomly assigned (1:1:1) using permuted block randomisation (block size of 12) to one of three polio vaccination schedules, with the first, second, and third doses given at ages 2 months, 3 months, and 4 months, respectively: sIPV-bOPV-bOPV (1sIPV+2bOPV group; current regimen), sIPV-sIPV-bOPV (2sIPV+1bOPV group), or sIPV-sIPV-sIPV (3sIPV group). The primary endpoint was the proportion of infants with seroconversion to each of the three poliovirus serotypes 1 month after the third dose. Serious and medically important adverse events were monitored for up to 30 days after each vaccination. We assessed immunity in the per-protocol population (all children who completed all three vaccinations and had pre-vaccination and post-vaccination laboratory data) and safety in all children who received at least one dose of study vaccine. This trial is registered with Clinicaltrials.gov, NCT03147560.

RESULTS

Between May 1, 2016, and Dec 1, 2017, we enrolled and randomly assigned 528 eligible infants to one of the three treatment groups (176 in each group); 473 infants (158 in the 1sIPV+2bOPV group, 152 in the 2sIPV+1bOPV group, and 163 in the 3sIPV group) were included in the per-protocol population. 100% seroconversion against poliovirus types 1 and 3 was observed in all three groups. Infants who received an immunisation schedule containing bOPV had significantly higher antibody titres against poliovirus types 1 and 3 than did the sIPV-only group (2048 in all three treatment groups; p<0·0001). Seroconversion against type 2 poliovirus was observed in 98 (62%) infants in the 1sIPV+2bOPV group, 145 (95%) infants in the 2sIPV+1bOPV group, and 161 (99%) infants in the 3sIPV group. No serious adverse events occurred during the study; 14 minor, transient adverse events were observed, with no significant differences across study groups.

INTERPRETATION

All three study schedules were well tolerated and highly immunogenic against poliovirus types 1 and 3. Schedules containing two or three sIPV doses had higher seroconversion rates against poliovirus type 2 than did the schedule with a single dose of sIPV. Our findings support inclusion of two sIPV doses in the routine poliovirus vaccination schedule in China to provide better protection against poliovirus type 2 than provided by the current regimen.

FUNDING

Chinese Center for Disease Control and Prevention and China National Biotec Group Company.

Poliovirus Type 2 Seroprevalence Following Full- or Fractional-Dose Inactivated Poliovirus Vaccine in the Period After Sabin Type 2 Withdrawal in Sri Lanka

BACKGROUND

In July 2016, Sri Lanka replaced 1 intramuscular dose of inactivated poliovirus vaccine (IPV) with 2 doses of intradermal fractional-dose IPV (fIPV) in its routine immunization schedule. We carried out a survey of seroprevalence of antipolio antibodies in children who received 2 fIPV doses and compared it with those who received 1 full IPV dose.

METHODS

Children born between March and December 2016 were randomly selected from 3 Sri Lankan districts (Colombo, Badulla, and Anuradhapura). Serum samples were collected and tested for presence of neutralizing antibodies to poliovirus types 1, 2, and 3.

RESULTS

Seroprevalence of antipolio antibodies was 100% in all districts for poliovirus type 1 and poliovirus type 3; it ranged between 90% and 93% for poliovirus type 2 (PV2) in children who received 1 full IPV dose and between 78% and 100% in those receiving 2 fIPV doses (P = .22). The median reciprocal titers of anti-PV2 antibodies were similar in children who received full-dose IPV and those who received fIPV (1:64 vs 1:45, respectively; P = .11).

CONCLUSIONS

Our study demonstrated not only that Sri Lanka succeeded in maintaining very high primary immunization coverage also but that it is feasible for a national immunization program to implement fIPV immunization and achieve high coverage with intradermal application. The seroprevalence of anti-PV2 antibodies did not decrease after the introduction of fIPV.

Immunogenicity and safety profile of a primary dose of bivalent oral polio vaccine given simultaneously with DTwP-Hb-Hib and inactivated poliovirus vaccine at the 4th visit in Indonesian infants

In this study, we aimed to evaluate the immunological protectivity of infants following four doses of bivalent oral polio vaccine (bOPV; Bio Farma), which were given simultaneously with DTwP-Hb-Hib (Pentabio®), along with one dose of inactivated poliovirus vaccine (IPV) at the fourth visit. A total of 143 newborn infants who fulfilled the inclusion criteria were enrolled and completed the study. Subjects received the first dose of bOPV at birth. On days 60, 90 and 120, bOPV was given simultaneously with Pentabio®. On day 120, one dose of IPV was also administered. Serum samples for serology analysis were collected before the first dose of bOPV (at day 0), before the second dose of bOPV (at day 60) and 30 days after the last dose of bOPV. In addition, the intensity, duration and relationship of each adverse event to the trial vaccines were assessed. Seroprotection rates after the fourth dose of bOPV were 100%, 91.6% and 99.3% for poliovirus P1, P2 and P3, respectively. Seroconversion rates after the fourth dose of bOPV were 100.0%, 93.3% and 100% for poliovirus P1, P2 and P3, respectively. There were no severe adverse events, and systemic reactions were generally mild during the 1-28 day post-vaccination period. Collectively, our findings indicate that bOPV given simultaneously with Pentabio® and one dose of IPV at the 4th visit was immunogenic and well tolerated.

Does Simultaneous Administration of Bivalent (Types 1 and 3) Oral Poliovirus Vaccine and Inactivated Poliovirus Vaccine Induce Mucosal Cross-immunity to Poliovirus Type 2?

Background

Inactivated poliovirus vaccine (IPV) alone does not induce mucosal immunity. However, it was hypothesized that administration of IPV together with bivalent (types 1+3) oral poliovirus vaccine (bOPV) may stimulate mucosal cross-immunity to poliovirus type 2 (PV2).

Methods

Cuban infants were randomized to receive either one dose of IPV (Arm A); one dose of IPV with bOPV (Arm B) at about 6 months of age or no vaccine (Arm C). Subjects were challenged with one dose of trivalent OPV (tOPV); they were about 7 months old in arms A and B, and about 3 months old in arm C at a time of the tOPV challenge. Sera were collected before vaccination and 30 days after tOPV challenge and tested for presence of poliovirus neutralizing antibodies; stool samples were collected at days 0, 7, 14, 21 and 49 post-challenge and tested for presence of poliovirus.

Results

We enrolled 333 children. Excretion of PV2 following tOPV challenge was highest on day 7 (75 [CI 95% = 65-82%], 68 [CI 95% = 58-75%] and 73 [CI 95% = 63-80%] for study arms A, B, and C respectively); excretion decreased with every subsequent stool sampling; no significant differences either in proportion of PV2 excretion or in its duration were observed between study arms.

Conclusions

There was no reduction in excretion of PV2 after tOPV challenge in children who had received IPV with bOPV when compared to those who had received IPV alone or no vaccine. Polio eradication program cannot assume any PV2 mucosal response with the current polio immunization schedule.

Clinical Trials Registration

The trial was registered with the Australian New Zealand Clinical Trials Registry and allocated trial number ACTRN12616000169448.

Immunogenicity of New Primary Immunization Schedules With Inactivated Poliovirus Vaccine and Bivalent Oral Polio Vaccine for the Polio Endgame: A Review

In May 2016, countries using oral polio vaccine for routine immunization switched from trivalent oral poliovirus vaccine (tOPV) to bivalent type 1 and 3 OPV (bOPV). This was done in order to reduce risks from type 2 vaccine-derived polioviruses (VDPV2) and vaccine-associated paralytic poliomyelitis (VAPP) and to introduce ≥1 dose of inactivated poliovirus vaccine (IPV) to mitigate post-switch loss of type 2 immunity. We conducted a literature review of studies that assessed humoral and intestinal immunogenicity induced by the newly recommended schedules. Differences in seroconversion rates were closely associated with both timing of first IPV administration and number of doses administered. All studies demonstrated high levels of immunity for types 1 and 3 regardless of immunization schedule. When administered late in the primary series, a second dose of IPV closed the humoral immunity gap against polio type 2 associated with a single dose. IPV doses and administration schedules appear to have limited impact on type 2 excretion following challenge.

Vaccination practices in dialysis patients: A narrative review

In a period of turmoil concerning vaccination practices, there is a serious conflict between scientifically reasonable, evidence-based guidelines and the far-fetched rumors or misconceptions concerning the vaccination practices in the general population. When a significant portion of the medical and paramedical personnel may be deliberately unvaccinated against common biological agents, achieving effective vaccination rates in the dialysis population may be complicated. Vaccination rates are unacceptably low in dialysis patients and seroconversion rates are even lower; further, serological follow-up is generally poor. The particularly anergic immune system of the advanced chronic kidney disease patients is partly a cause of both high rates of infection and low rates of seroconversions. This narrative review is an effort to summarize current knowledge concerning the vaccination practices in dialysis patients with some specific recommendations based on these facts. Of particular interest is a new vaccine, the Zoster Recombinant, Adjuvanted Vaccine (Shingrix), which we will include in our discussion.

Evaluation of vaccine derived poliovirus type 2 outbreak response options: A randomized controlled trial, Karachi, Pakistan

Background

Outbreaks of circulating vaccine derived polioviruses type 2 (cVDPV2) remain a risk to poliovirus eradication in an era without live poliovirus vaccine containing type 2 in routine immunization. We evaluated existing outbreak response strategies recommended by the World Health Organization (WHO) for control of cVDPV2 outbreaks.

Methods

Seronegative children for poliovirus type 2 (PV2) at 22 weeks of life were assigned to one of four study groups and received respectively (1) one dose of trivalent oral poliovirus vaccine (tOPV); (2) monovalent OPV 2 (mOPV2); (3) tOPV together with a dose of inactivated poliovirus vaccine (IPV); or (4) mOPV2 with monovalent high-potency IPV type 2. Stool and blood samples were collected and assessed for presence of PV2 (stool) and anti-polio antibodies (sera).

Results

We analyzed data from 265 children seronegative for PV2. Seroconversion to PV2 was achieved in 48, 76, 98 and 100% in Groups 1–4 respectively. mOPV2 was more immunogenic than tOPV alone (p < 0.001); and OPV in combination with IPV was more immunogenic than OPV alone (p < 0.001). There were 33%, 67%, 20% and 43% PV2 excretors in Groups 1–4 respectively. mOPV2 resulted in more prevalent shedding of PV2 than when tOPV was used (p < 0.001); and tOPV together with IPV resulted in lower excretion of PV2 than tOPV alone (p = 0.046).

Conclusion

mOPV2 was a more potent vaccine than tOPV. Adding IPV to OPV improved immunological response; adding IPV also seemed to have shortened the duration of PV2 shedding. mIPV2 did not provide measurable improvement of immune response when compared to conventional IPV. WHO recommendation to use mOPV2 as a vaccine of first choice in cVDPV2 outbreak response was supported by our findings.

Clinical Trial registry number: NCT02189811.