Immunogenicity and safety of a second heterologous booster dose of NVX-CoV2373 (TAK-019) in healthy Japanese adults who had previously received a primary series of COVID-19 mRNA vaccine: Interim analysis report of a phase 3 open-label trial

BACKGROUND

The phase 3, single-arm, open-label TAK-019-3001 study assessed two heterologous booster doses of NVX-CoV2373 administered 5 months apart in healthy Japanese adults who had completed a primary series of a COVID-19 mRNA vaccine 6-12 months previously. In the main part of this study, a first booster induced rapid and robust anti-SARS-CoV-2 immune responses, addressing waning immunity in participants.

METHODS

This interim analysis evaluated the immunogenicity and safety of a second booster in the extension part of this study including comparisons with the first booster. Immunogenicity was assessed on extension day (ED) 1 (before vaccination) and ED15. Solicited and unsolicited adverse events occurring in the 7 and 28 days, respectively, after vaccination were assessed.

RESULTS

Of the 150 participants who received a first NVX-CoV2373 booster, 129 were administered a second booster on ED1. Participant characteristics were consistent between the main and extension parts of the study. Titres of anti-SARS-CoV-2 rS serum immunoglobulin G and serum neutralizing antibodies against the SARS-CoV-2 ancestral strain at ED15 were 4.0- and 3.0-fold higher, respectively, than those observed 5 months after the first booster on ED1, and 3.0- and 1.4-fold higher, respectively, than those observed 14 days after the first booster on day 15. The proportions of participants who experienced solicited local and systemic adverse events (AEs) in the 7 days after the second booster were 73.6 % and 51.2 %, respectively: most were of grade 2 severity or lower. Seven percent of participants experienced unsolicited AEs in the 28 days after the second booster: all were unrelated to the treatment. There were no deaths or AEs leading to study discontinuation.

DISCUSSION

A second heterologous NVX-CoV2373 booster in healthy Japanese adults induced more robust anti-SARS-CoV-2 immune responses than the first booster. The second booster was well tolerated. No new safety concerns were identified.

Should we vaccinate during an active rheumatic disease?

Timing of vaccination and its relationship with concomitant immunosuppressive therapy has been a matter of debate in the field of AutoImmune Inflammatory Rheumatic Diseases (AIIRD). Vaccination is crucial in the prevention of infections, which, in the setting of AIIRD, are known risk factors for disease flare and expose patients to increase risk of complications and mortality. As evidenced from real-life studies, vaccines do not significantly affect disease activity. Conversely, disease activity (especially in Systemic Lupus Erythematosus) may predict for vaccine response: high disease activity correlates with decreased seroconversion. For this reason, according to the EULAR 2019 recommendation, vaccination should preferably be administered during quiescent AIIRD. Beside disease activity, background immunosuppressive therapy should be considered when performing vaccination, as different Disease Modifying Anti-Rheumatic Drugs (DMARDs) decrease vaccine immunogenicity. AIIRD patients should be vaccinated, independently from the vaccine type, before starting immunosuppression. If the patient is on active immunosuppressive therapy, the best window of opportunity to boost vaccine response is during AIIRD quiescence, as low disease activity increases seroconversion and allows safe immunosuppressant spacing. In conclusion, the majority of AIIRD patients should receive vaccination, preferably during quiescent disease and taking into consideration immunosuppressant spacing.

A Brighton Collaboration standardized template with key considerations for a benefit/risk assessment for the Novavax COVID-19 Vaccine (NVX-CoV2373), a recombinant spike protein vaccine with Matrix-M adjuvant to prevent disease caused by SARS-CoV-2 viruses

Novavax, a global vaccine company, began evaluating NVX-CoV2373 in human studies in May 2020 and the pivotal placebo-controlled phase 3 studies started in November 2020; five clinical studies provided adult and adolescent clinical data for over 31,000 participants who were administered NVX-CoV2373. This extensive data has demonstrated a well-tolerated response to NVX-CoV2373 and high vaccine efficacy against mild, moderate, or severe COVID-19 using a two-dose series (Dunkle et al., 2022) [1], (Heath et al., 2021) [2], (Keech et al., 2020) [3], (Mallory et al., 2022) [4]. The most common adverse events seen after administration with NVX-CoV2373 were injection site tenderness, injection site pain, fatigue, myalgia, headache, malaise, arthralgia, nausea, or vomiting. In addition, immunogenicity against variants of interest (VOI) and variants of concern (VOC) was established with high titers of ACE2 receptor-inhibiting and neutralizing antibodies in these studies (EMA, 2022) [5], (FDA, 2023) [6]. Further studies on correlates of protection determined that titers of anti-Spike IgG and neutralizing antibodies correlated with efficacy against symptomatic COVID-19 established in clinical trials (p < 0.001 for recombinant protein vaccine and p = 0.005 for mRNA vaccines for IgG levels) (Fong et al., 2022) [7]. Administration of a booster dose of the recombinant protein vaccine approximately 6 months following the primary two-dose series resulted in substantial increases in humoral antibodies against both the prototype strain and all evaluated variants, similar to or higher than the antibody levels observed in phase 3 studies that were associated with high vaccine efficacy (Dunkle et al., 2022) [1], (Mallory et al., 2022) [4]. These findings, together with the well tolerated safety profile, support use of the recombinant protein vaccine as primary series and booster regimens.

Serologic immunogenicity and safety of Herpes Zoster subunit vaccine in patients with Rheumatoid Arthritis receiving Janus Kinase inhibitors

OBJECTIVE

Patients with rheumatoid arthritis (RA) treated with Janus Kinase inhibitors (JAKi) are at increased risk of Herpes Zoster (HZ). The objective of this study was to investigate serological immunogenicity and safety of the HZ subunit (HZ/su) vaccine in RA patients treated with JAKi, for which little is known.

METHODS

RA patients treated with JAKi (n = 82) at the Department of Rheumatology, Skåne University Hospital, Sweden, and healthy controls (n = 51) received two doses of the HZ/su vaccine (Shingrix). Vaccine-specific antibody responses were analysed using indirect enzyme-linked immunosorbent assay (ELISA). Post-vaccination antibody levels were compared between patients and controls using analysis of covariance. Potential predictors for vaccine response were investigated using a multivariable linear regression analysis. Self-reported adverse events (AEs) and changes in RA disease activity were analysed.

RESULTS

Following vaccination, vaccine-specific antibody levels increased significantly in both patients and controls (p< 0.0001). 80.5% of patients and 98.0% of controls achieved a ≥ 4-fold increase in antibody levels. Post-vaccination antibody levels were lower in patients than controls (ratio 0.44, 95% CI 0.31-0.63), and lower in patients receiving JAKi+Methotrexate than JAKi monotherapy (ratio 0.43, 95% CI 0.24-0.79). AEs, mostly mild/moderate, were common. One patient developed HZ and six patients (6.5%) had increased RA disease activity following vaccination.

CONCLUSION

The HZ/su vaccine was serologically immunogenic in most RA patients treated with JAKi. Moreover, the vaccine had an acceptable safety profile. These results support recommendations for usage of the HZ/su vaccine in this vulnerable population.

TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT03886038.

Immunogenicity and safety of a fourth homologous dose of NVX-CoV2373

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has significantly reduced the efficacy of some approved vaccines. A fourth dose of NVX-CoV2373 (5 µg SARS-CoV-2 recombinant spike [rS] protein + 50 µg Matrix-M™ adjuvant; Novavax, Gaithersburg, MD) was evaluated to determine induction of cross-reactive antibodies to variants of concern. A phase II randomized study (NCT04368988) recruited participants in Australia and the United States to assess a primary series of NVX-CoV2373 followed by two booster doses (third and fourth doses at 6-month intervals) in adults 18-84 years of age. The primary series was administered when the SARS-CoV-2 ancestral strain was prevalent and the third and fourth doses while the Alpha and Delta variants were prevalent in AUS and US. Local/systemic reactogenicity was assessed the day of vaccination and for 6 days thereafter. Unsolicited adverse events (AEs) were reported. Immunogenicity was measured before, and 14 days after, fourth dose administration, using anti-spike serum immunoglobulin G (IgG) and neutralization assays against ancestral SARS-CoV-2 strain and Omicron sublineages. Among 1283 enrolled participants, 258 were randomized to receive the two-dose primary series, of whom 104 received a third dose, and 45 received a fourth dose of NVX-CoV2373. The incidence of local/systemic reactogenicity events increased after the first three doses of NVX-CoV2373 and leveled off after dose 4. Unsolicited AEs were reported in 9 % of participants after dose 4 (none of which were severe or serious). Anti-rS IgG levels and neutralization antibody titers increased following booster doses to a level approximately four-fold higher than that observed after the primary series, with a progressively narrowed gap in response between the ancestral strain and Omicron BA.5. A fourth dose of NVX-CoV2373 enhanced immunogenicity for ancestral and variant SARS-CoV-2 strains without increasing reactogenicity, indicating that updates to the vaccine composition may not be currently warranted.

Vaccinomics: A scoping review

BACKGROUND

This scoping review summarizes a key aspect of vaccinomics by collating known associations between heterogeneity in human genetics and vaccine immunogenicity and safety.

METHODS

We searched PubMed for articles in English using terms covering vaccines routinely recommended to the general US population, their effects, and genetics/genomics. Included studies were controlled and demonstrated statistically significant associations with vaccine immunogenicity or safety. Studies of Pandemrix®, an influenza vaccine previously used in Europe, were also included, due to its widely publicized genetically mediated association with narcolepsy.

FINDINGS

Of the 2,300 articles manually screened, 214 were included for data extraction. Six included articles examined genetic influences on vaccine safety; the rest examined vaccine immunogenicity. Hepatitis B vaccine immunogenicity was reported in 92 articles and associated with 277 genetic determinants across 117 genes. Thirty-three articles identified 291 genetic determinants across 118 genes associated with measles vaccine immunogenicity, 22 articles identified 311 genetic determinants across 110 genes associated with rubella vaccine immunogenicity, and 25 articles identified 48 genetic determinants across 34 genes associated with influenza vaccine immunogenicity. Other vaccines had fewer than 10 studies each identifying genetic determinants of their immunogenicity. Genetic associations were reported with 4 adverse events following influenza vaccination (narcolepsy, GBS, GCA/PMR, high temperature) and 2 adverse events following measles vaccination (fever, febrile seizure).

CONCLUSION

This scoping review identified numerous genetic associations with vaccine immunogenicity and several genetic associations with vaccine safety. Most associations were only reported in one study. This illustrates both the potential of and need for investment in vaccinomics. Current research in this field is focused on systems and genetic-based studies designed to identify risk signatures for serious vaccine reactions or diminished vaccine immunogenicity. Such research could bolster our ability to develop safer and more effective vaccines.

The effectiveness of mRNA vaccines to prevent SARS-CoV-2 infection and hospitalisation for COVID-19 according to the time elapsed since their administration in health professionals in the Valencian Autonomous Community (Spain)

The objective was to understand the effectiveness of the BNT162b2 and mRNA-1273 vaccines against SARS-CoV-2 in health professionals(HPs) in the Valencian Autonomous Community(Spain) who had completed a full vaccination regimen, both in terms of preventing infections and avoiding hospitalisations, according to the time elapsed since the vaccine administration. Case-controlled study with negative test results. HPs who had undergone at least one PCR or antigen(Ag) active infection diagnostic test(AIDT) to rule out SARS-CoV-2 infection between 25 January and 18 July 2021 were included. HPs with positive AIDT result were considered as cases and those with a negative result controls. Adjusted vaccine effectiveness(VEa) to prevent SARS-CoV-2 infection and its 95% confidence interval(95% CI) were calculated using the formula VEa = (1 - OR) × 100. The VEa for the prevention of SARS-CoV-2 infection 12 to 120 days after completing the full two-dose vaccine regimen was 91.6%(95%CI[89.6%,93.2%]) for the BNT162b2 vaccine and 95.2%(95%CI[88.3%,98.1%]) for the mRNA-1273 vaccine. After 120 days the VEa was 71.5%(95%CI[67.0%,75.5%]) for the BNT162b2 vaccine and 88.3%(95%CI[75.7,94.4%]) for the mRNA-1273 vaccine. The VEa for prevention of hospitalisation for COVID-19 for the complete two-dose regimen of mRNA vaccines (BNT162b2 and mRNA-1273) was 96.8%(95%CI[76.1%,99.6%]). The administration of the complete regimen of the BNT162b2 and mRNA-1273 vaccine against SARS-CoV-2 was highly effective for the prevention of COVID-19 cases in HPs when 12 to 120 days had elapsed since the second dose. However, said effectiveness decreased as time from the vaccine administration elapsed, although it was maintained for the prevention of hospitalisation of HPs.

Immunogenicity after outbreak response immunization activities among young healthcare workers with secondary vaccine failure during the measles epidemic in Korea, 2019

BACKGROUND

Despite high vaccination coverage, measles outbreaks have been reported in measles elimination countries, especially among healthcare workers in their 20 and 30 s. This study was designed to identify measles-susceptible individuals and to evaluate whether primary or secondary vaccine failure occurred during measles outbreak response immunization (ORI) activities.

METHODS

The study population was divided into three groups as follows: natural immunity group (Group 1), vaccine-induced immunity group (Group 2), and vaccine failure group (Group 3). We evaluated the immunogenicity of measles among healthcare workers using three methods-enzyme-linked immunoassays, plaque reduction neutralization tests, and avidity assays. The results were assessed at baseline, 4 weeks after, and 6 months after the completion of measles-mumps-rubella (MMR) vaccination.

RESULTS

In total, 120 subjects were enrolled, with 40 subjects in each group. The median age of Group 3 was 29 years, which was significantly lower than that of the other groups. The baseline negative measles virus (MeV) IgG in Group 3 increased to a median value of 165 AU/mL at 4 weeks after ORI and was lower than that in Groups 1 and 2. The median neutralizing antibody titer was highest in Group 1, and this was significantly different from that in Group 2 or Group 3 at 4 weeks (944 vs. 405 vs. 482 mIU/mL, P = 0.001) and 6 months (826 vs. 401 vs. 470, P = 0.011) after ORI. The rates of high MeV avidity IgG were highest in Group 2, and these were significantly different from those in Groups 1 or 3 at 4 weeks (77.5 vs. 90% vs. 88.6%, P = 0.03) and 6 months (81 vs. 94.8 vs. 82.1%, P = 0.01) after ORI.

CONCLUSIONS

Considering the MeV-neutralizing antibodies and IgG avidity after MMR vaccination in measles-susceptible group, vaccine failure is inferred as secondary vaccine failure, and further data regarding the maintenance of immunogenicity are needed based on long-term data. The MeV-neutralizing antibody levels were highest in the natural immunity group, and the primary vaccine-induced immunity group showed the highest rates of high MeV IgG avidity.

Cellular and humoral responses to SARS-CoV-2 vaccination in immunosuppressed patients

OBJECTIVE

SARS-CoV-2 vaccinations have demonstrated vaccine-immunogenicity in healthy volunteers, however, efficacy in immunosuppressed patients is less well characterised. There is an urgent need to address the impact of immunosuppression on vaccine immunogenicity.

METHODS

Serological, T-cell ELISpot, cytokines and immunophenotyping were used to assess vaccine responses (either BNT162b2 mRNA or ChAdOx1 nCoV-19) in double-vaccinated patients receiving immunosuppression for renal transplants or haematological malignancies (n = 13). Immunological responses in immunosuppressed patients (VACC-IS) were compared to immunocompetent vaccinated (VACC-IC, n = 12), unvaccinated (UNVACC, n = 11) and infection-naïve unvaccinated (HC, n = 3) cohorts.

RESULTS

No significant different differences in T-cell responses were observed between VACC-IS and VACC-IC (92%) to spike-peptide (S) stimulation. UNVACC had the highest T-cell non-responders (n = 3), whereas VACC-IC and VACC-IS both had one T-cell non-responder. No significant differences in humoral responses were observed between VACC-IC and VACC-IS, with 92% (12/13) of VACC-IS patients demonstrating seropositivity. One VACC-IS failed to seroconvert, however had detectable T-cell responses. All VACC-IC participants were seropositive for anti-spike antibodies. VACC-IS and VACC-IC participants elicited strong Th1 cytokine response with immunodominance towards S-peptide. Differences in T-cell immunophenotyping were seen between VACC-IS and VACC-IC, with lower CD8⁺ activation and T-effector memory phenotype observed in VACC-IS.

CONCLUSION

SARS-CoV-2 vaccines are immunogenic in patients receiving immunosuppressive therapy, with responses comparable to vaccinated immunocompetent participants. Lower humoral responses were seen in patients treated with B-cell depleting therapeutics, but with preserved T-cell responses. We suggest further work to correlate both protective immunity and longevity of these responses in both healthy and immunosuppressed patients.

[High-dose trivalent influenza vaccine: safety and immunogenicity]

Las personas mayores son uno de los colectivos que más sufren los efectos de la gripe estacional. Aunque la vacuna antigripal es efectiva a la hora de prevenir la infección por el virus de la gripe y sus complicaciones, no resulta tan efectiva en personas de edad avanzada debido al fenómeno de inmunosenescencia asociado a la edad. Desde 2009 existe en EE. UU. una vacuna antigripal trivalente de alta dosis aprobada para la inmunización de personas ≥ 65 años con una concentración de antígeno cuatro veces mayor que la vacuna estándar. Múltiples ensayos clínicos llevados a cabo a lo largo de distintas temporadas, y mediante diferentes metodologías, han demostrado que la vacuna antigripal trivalente de alta dosis no solo es más efectiva, sino que además presenta un perfil de seguridad similar y es más inmunogénica que la vacuna de dosis estándar en la prevención de la gripe y sus complicaciones en personas de avanzada edad. En este documento se hace una revisión de la evidencia científica actual sobre la seguridad e inmunogenicidad de la vacuna antigripal de alta dosis en personas ≥ 65 años, y se incluye información de ensayos clínicos aleatorizados, estudios observacionales con datos de práctica clínica real y revisiones sistemáticas y metaanálisis.

Pertussis in Lao PDR: Seroprevalence and disease

OBJECTIVES

Pertussis is a debilitating vaccine-preventable infection. The aim of this study was to determine susceptibility and exposure to pertussis in Lao PDR in different age groups and subpopulations.

METHODS

A total 3072 serum samples were obtained from different cohorts: children with documented vaccination, pre-schoolers, schoolchildren, blood donors, healthcare workers (HCWs), and pregnant women and paired cord blood. Samples were tested for anti-pertussis toxin IgG antibodies. A history of Bordetella pertussis exposure was defined according to antibody titres. Four hundred and seventy-five throat swabs and nasopharyngeal aspirates were analysed by PCR for the presence of B. pertussis in symptomatic children at the Children's Hospital in Vientiane.

RESULTS

Overall pertussis seroprevalence was 57.5%. The prevalence of titres indicating acute infection or recent vaccination or infection/vaccination within the last 12 months ranged from 7.4% (100/1356) in adults to 21.4% (25/117) in pre-schoolers (age 1-5 years). B. pertussis was detected in 1.05% (5/475) of children with respiratory symptoms in Vientiane Capital.

CONCLUSIONS

It is suggested that routine childhood vaccination, in particular outreach, as well as vaccination of HCWs should be strengthened. A childhood booster and vaccination of pregnant mothers should be considered. There is also a need to improve reporting and to introduce pertussis testing in at least one central facility.

Safety and immunogenicity of inactivated monovalent influenza A/H1N1 vaccine candidate manufactured in Vietnam

We tested a new A/H1N1 inactivated influenza vaccine (IIV) manufactured by Institute of Vaccines and Medical Biologics (IVAC), Vietnam in 48 adults in a Phase 1, double-blinded, randomized, placebo-controlled trial. Two doses of unadjuvanted vaccine or placebo were administered three weeks apart. The vaccine was well tolerated with only transient mild local reactions and low-grade fever in a small proportion of the subjects. One serious adverse event considered unrelated to the study product was reported. The IVAC vaccine proved to be highly immunogenic with 91 percent (95% CI: 0.78, 1) of the subjects developing a ≥4 fold immune responses by hemagglutination inhibition (HAI) assay, and 96 percent (95% CI: 0.78, 1) by the microneutralization (MN) assay. Post-vaccination geometric mean titers (GMTs) were 283.7 (95% CI: 161.7, 497.5) in the HAI and 725.7 (95% CI: 411.3, 1280.3) in the MN assay. These promising results merit further development of the vaccine. ClinicalTrials.gov number: NCT01507779.

Immunogenicity of a bivalent killed thimerosal-free oral cholera vaccine, Euvichol, in an animal model

PURPOSE

An oral cholera vaccine (OCV), Euvichol, with thimerosal (TM) as preservative, was prequalified by the World Health Organization (WHO) in 2015. In recent years, public health services and regulatory bodies recommended to eliminate TM in vaccines due to theoretical safety concerns. In this study, we examined whether TM-free Euvichol induces comparable immunogenicity to its TM-containing formulation in animal model.

MATERIALS AND METHODS

To evaluate and compare the immunogenicity of the two variations of OCV, mice were immunized with TM-free or TM-containing Euvichol twice at 2-week interval by intranasal or oral route. One week after the last immunization, mice were challenged with Vibrio cholerae O1 and daily monitored to examine the protective immunity against cholera infection. In addition, serum samples were obtained from mice to measure vibriocidal activity and vaccine-specific IgG, IgM, and IgA antibodies using vibriocidal assay and enzyme-linked immunosorbent assay, respectively.

RESULTS

No significant difference in immunogenicity, including vibriocidal activity and vaccine-specific IgG, IgM, and IgA in serum, was observed between mice groups administered with TM-free and -containing Euvichol, regardless of immunization route. However, intranasally immunized mice elicited higher levels of serum antibodies than those immunized via oral route. Moreover, intranasal immunization completely protected mice against V. cholerae challenge but not oral immunization. There was no significant difference in protection between two Euvichol variations.

CONCLUSION

These results suggested that TM-free Euvichol could provide comparable immunogenicity to the WHO prequalified Euvichol containing TM as it was later confirmed in a clinical study. The pulmonary mouse cholera model can be considered useful to examine in vivo the potency of OCVs.

Fever prophylaxis can reduce vaccine responses: A caution

Prophylactic administration of antipyretic/analgesic drugs, started at the time of immunization and repeated 6 and 12 hours later, is sometimes undertaken to reduce postimmunization fever and irritability in infants. Two recent studies showed that such prophylaxis can reduce immune responses to some infant vaccines, warranting judicious use. In contrast, implementing treatment 6 hours or more after immunization had no effect on vaccine responses and would reduce drug exposure of asymptomatic infants.

The safety and immunogenicity of Quadrivalent HPV (qHPV) vaccine in systemic lupus erythematosus

OBJECTIVE

This study evaluated the safety and immunogenicity of qHPV vaccine in SLE.

METHODS

Subjects: 34 women ages 19-50years (yrs.) with mild to moderate SLE & minimally active or inactive SLE received qHPV vaccine at the standard dosing schedule.

EXCLUSION CRITERIA

active SLE disease (SELENA-SLEDAI>2), history of severe SLE disease, deep venous thrombosis, on >400mg/day of hydroxychloroquine, on >15mg/day of prednisone, or active infections. Patients were monitored for adverse events (AE), SLE flare, generation of thrombogenic antibodies and thrombosis. Antibody (Ab) levels to HPV 6, 11, 16 & 18 were measured by HPV competitive Luminex Immunoassay and Geometric Mean Titers (GMTs) were calculated for each HPV type. Seroconversion was assessed for those seronegative at baseline.

RESULTS

The women in the study: African-American (79%), mean age=38.1years, mean age at diagnosis of SLE=28.6years, 35.3% had a history of smoking, 91% had 4 or more sexual partners, 50% had a history of sexually transmitted diseases, and 27.3% used condoms on a regular basis. Vaccine site reactions (VSRs) occurred in 62%, all mild. Ninety-seven percent experienced at least 1 non vaccine adverse event (nvAE) with a total of 493 nvAEs in 33 patients, of which 90% were mild and none were related to vaccine or SLE. There were 9 serious AEs, none were related to vaccine or SLE, all resolved. No patient experienced an SLE flare, thrombosis, or generation of thrombogenic antibodies. Seroconversion rate was 100% with mean GMTs comparable to Gardasil® package insert data.

CONCLUSION

In this SLE vaccine study, qHPV vaccine was generally safe, well tolerated, and highly immunogenic. This clinical trial is registered on Clinical Trials.gov under number, NCT01741012 and was conducted under the FDA IND BB14113.

Suitable hepatitis B vaccine for adult immunization in China

The aim of this study was to evaluate, in adults, the immunogenicity of six hepatitis B vaccines with different doses or different manufacturers in the Chinese market and to provide evidence to support adult hepatitis B vaccination. Participants were randomly divided into six groups (I–VI). Six vaccines (4 at 10 μg/dose and 2 at 20 μg/dose) were administered intramuscularly to healthy adults at 0, 1 and 6 month intervals. All participants (16–50 years) who were negative for any hepatitis B virus serological markers were vaccinated. Anti-HBs levels were assessed 1 month and 1 year after the third vaccination. The anti-HBs seroconversion rate (anti-HBs >10mIU/ml) was 99.4 % (99.9 % for 10 μg dose groups and 97.9 % for 20 μg dose groups) 1 month after the third vaccination, and the anti-HBs seroreversion rate was 77.0 % (75.3 and 82.6 %) 1 year after the third vaccination (n = 1036). One month after completing the vaccinations, the seroconversion rates were not significantly different (100.0, 100.0, 99.6, 100.0 %) for the four 10 μg dose and two 20 μg dose groups (99.1, 96.9 %). One year after the third vaccination, the group II positive rate was significantly higher than the other three 10 μg dose groups, and the group VI positive rate was significantly higher than the other 20 μg dose group. Groups II and VI showed a significantly higher positive rate and anti-HBs geometric mean titer (GMT) than the other groups. The anti-HBs level declined with increasing age, and the seroreversion rate and GMT decreased over time. All six vaccines had high anti-HBs seroconversion rates and good immunization effects. The 10 μg dose vaccine (Dalian High-Tech) and the 20 μg dose vaccine (GlaxoSmithKline) are recommended for adults.

Low and disparate seroprotection after pentavalent childhood vaccination in the Lao People's Democratic Republic: a cross-sectional study

OBJECTIVE

In Lao People's Democratic Republic, the high burden of vaccine-preventable diseases is thought to be mainly due to low vaccine coverage. We investigated the seroprotective response against diphtheria-tetanus-whole cell pertussis-hepatitis B-Haemophilus influenzae type b (DTPw-HepB-Hib) vaccine in children.

METHODS

Serum was collected from 1131 children aged 9 to 50 months and their mothers in a cross-sectional study between December 2013 and July 2014. All children had records of three injections of the DTPw-HepB-Hib vaccine. Serum was analysed for hepatitis B surface antigen (HBsAg), anti-HBsAg (anti-HBs), anti-hepatitis B virus core antigen (anti-HBc), anti-diphtheria and anti-tetanus antibodies. Stool samples were collected for detection of parasites. Demographic and nutritional information were also obtained.

RESULTS

Protective levels of anti-HBs antibodies were found in 394 (37.9%) of 1039 children; 529 (55.7%) of 950 and 809 (85.2%) of 950 children were seroprotected against diphtheria and tetanus. Time since vaccination, age, home birth and malnutrition only partially explained the poor vaccine responses. Overall, 81 (7.8%) of 1039 children and 445 (40.3%) of 1105 of mothers were anti-HBc positive. Ten (1.0%) of 1039 of the children and 77 (7.0%) of 1105 of the mothers were HBsAg carriers.

CONCLUSIONS

After a full documented course of vaccination, seroprotective rates were unusually low and disparate against components of the pentavalent vaccine. These can only partially be explained by the negative predictors identified. Although many children had been infected, only few were chronic carriers of HBsAg. Our study demonstrates an urgent need to monitor the serologic response to vaccination, particularly in resource-poor countries.

Impact of enterovirus and other enteric pathogens on oral polio and rotavirus vaccine performance in Bangladeshi infants

BACKGROUND

Oral polio vaccine (OPV) and rotavirus vaccine (RV) exhibit poorer performance in low-income settings compared to high-income settings. Prior studies have suggested an inhibitory effect of concurrent non-polio enterovirus (NPEV) infection, but the impact of other enteric infections has not been comprehensively evaluated.

METHODS

In urban Bangladesh, we tested stools for a broad range of enteric viruses, bacteria, parasites, and fungi by quantitative PCR from infants at weeks 6 and 10 of life, coincident with the first OPV and RV administration respectively, and examined the association between enteropathogen quantity and subsequent OPV serum neutralizing titers, serum rotavirus IgA, and rotavirus diarrhea.

RESULTS

Campylobacter and enterovirus (EV) quantity at the time of administration of the first dose of OPV was associated with lower OPV1-2 serum neutralizing titers, while enterovirus quantity was also associated with diminished rotavirus IgA (-0.08 change in log titer per tenfold increase in quantity; P=0.037), failure to seroconvert (OR 0.78, 95% CI: 0.64-0.96; P=0.022), and breakthrough rotavirus diarrhea (OR 1.34, 95% CI: 1.05-1.71; P=0.020) after adjusting for potential confounders. These associations were not observed for Sabin strain poliovirus quantity.

CONCLUSION

In this broad survey of enteropathogens and oral vaccine performance we find a particular association between EV carriage, particularly NPEV, and OPV immunogenicity and RV protection. Strategies to reduce EV infections may improve oral vaccine responses. ClinicalTrials.gov Identifier: NCT01375647.

Use of placebos in Phase 1 preventive HIV vaccine clinical trials

Phase 1 preventive HIV vaccine trials are often designed as randomized, double-blind studies with the inclusion of placebo recipients. Careful consideration is needed to determine when the inclusion of placebo recipients is highly advantageous and when it is optional for achieving the study objectives of assessing vaccine safety, tolerability and immunogenicity. The inclusion of placebo recipients is generally important to form a reference group that ensures fair evaluation and interpretation of subjective study endpoints, or endpoints whose levels may change due to exposures besides vaccination. In some settings, however, placebo recipients are less important because other data sources and tools are available to achieve the study objectives.

Optimisation of a functional mycobacterial growth-inhibition assay to improve its suitability for infant TB vaccine studies

The development of vaccines against tuberculosis continues to be hindered by the lack of correlates of protection. Immunity to Mycobacterium tuberculosis (M.tb) infection relies predominantly on cell mediated response, which is routinely measured using a read-out of host cytokine profiles. However, to date none of the cytokine profiles have been found to predict protection. A number of functional in vitro approaches that measure growth of mycobacteria pre- and post-vaccination as a potential functional surrogate marker for vaccine take have been developed. The use of a reporter-gene tagged BCG-lux assay measuring the viability of mycobacteria in whole blood samples has previously been described by our group to assess vaccine immunogenicity. Since only very small blood samples are usually available in paediatric studies, we now report a modification of the BCG-lux assay to reduce the volume required and make it more field-friendly. Our results show that a 2-fold reduction in blood volume made no significant difference to bacterial growth ratios, used as the main read-out. These results confirm the suitability of the BCG-lux assay for functional studies of vaccine immunogenicity and immunopathogenesis in young children and could play a role in late-phase TB vaccine trials of novel candidates.

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A 2-fold reduction in blood volume can now be used in a functional BCG-lux assay.

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This growth-restriction assay is a useful tool for vaccine assessment.

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Reduction in blood volumes will aid its use in trials of TB vaccines in infants.