The efficacy, effectiveness, and immunogenicity of influenza vaccines in Africa: a systematic review

Safety and immunogenicity of an acellular pertussis vaccine containing genetically detoxified pertussis toxin administered to pregnant women living with and without HIV and their newborns (WoMANPOWER): a randomised controlled trial in Uganda

BACKGROUND

Immunisation in pregnancy against pertussis can reduce severe disease in infancy. There are few data on the safety and immunogenicity of vaccines given to pregnant women living with HIV and their infants. We aimed to describe the safety and immunogenicity of a tetanus-diphtheria-acellular pertussis (TdaP) vaccine containing genetically detoxified pertussis toxin given to pregnant women living with HIV and the effect of the vaccine on infant whole-cell pertussis vaccine responses.

METHODS

We conducted an observer-blind, randomised, phase 2, multicentre, non-inferiority trial evaluating safety and immunogenicity of a vaccine containing genetically detoxified acellular pertussis in pregnant women living with HIV in Uganda. Women aged at least 18 years between 16 weeks and 26 weeks of gestation were randomly assigned to receive the tetanus-diphtheria (Td) vaccine or TdaP vaccine. Stratified block randomisation using blocks of four with a 1:1:1:1 ratio stratified by participant HIV status was used to distribute participants into equal groups (50 participants per group for a total of 200 participants). The intervention was a 0·5 mL single intramuscular dose of TdaP vaccine. Td or TdaP vaccination was randomly assigned to different clinic days using randomisation software. Primary immunogenicity endpoints were anti-pertussis toxin and anti-filamentous haemagglutinin IgG concentrations in infants at delivery and 18 weeks following three doses of a whole-cell pertussis containing vaccine. This study is registered at ClinicalTrials.gov, NCT04589312.

FINDINGS

Between Oct 28, 2020, and May 21, 2021, 438 pregnant women were screened and 181 were randomly assigned: 90 to TdaP vaccine (40 HIV-positive participants and 50 HIV-negative participants) and 91 to Td vaccine (41 HIV-positive participants and 50 HIV-negative participants). All participants received Td, and 4 weeks later, 177 received either Td or TdaP. 32 serious adverse events occurred, none related to the study vaccine. At delivery, anti-pertussis toxin IgG concentrations for TdaP versus Td were superior in infants who were HIV-exposed but uninfected (geometric mean ratio 9·61, 95% CI 5·21-17·74) and HIV-unexposed infants (21·6, 11·2-41·7). In infants at 18 weeks, anti-pertussis toxin IgG concentrations for TdaP versus Td-vaccinated mothers were significantly lower for both infants who were HIV-exposed but uninfected (0·19, 0·09-0·43) and infants who were not HIV-exposed (0·17, 0·08-0·33). Serum bactericidal antibody generation following whole-cell pertussis vaccination in infants was not affected.

INTERPRETATION

TdaP was safe and immunogenic in pregnant women living with HIV and their infants. TdaP provided superior anti-pertussis toxin IgG concentrations at delivery. Following routine vaccination with whole-cell pertussis vaccine, infants born to women receiving the TdaP vaccine had lower anti-pertussis toxin IgG concentrations than infants born to women receiving Td. In the absence of a correlate of protection against pertussis disease, the clinical significance of this finding is unclear.

FUNDING

Medical Research Council Joint Clinical Trials, Canadian Institutes of Health Research, and British Columbia Children's Hospital Research Institute.

Comparative assessment of immunogenicity of recombinant insulin Aspart from BioGenomics and its originator NovoRapid® in adult patients with type 2 diabetes mellitus

OBJECTIVES

To assess and compare the immunogenicity of recombinant Insulin Aspart [manufactured by BioGenomics Limited (BGL-ASP)] with its originator NovoRapid® (manufactured by Novo Nordisk) in adult patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

BGL-IA-CTP301 study was a randomized, open label, parallel group, multicenter phase-III clinical study to compare the efficacy and safety of recombinant Insulin Aspart 100 U/mL [manufactured by BioGenomics Limited (BGL-ASP)] with its reference medicinal product (RMP); NovoRapid® [manufactured by Novo Nordisk], in adult patients with Type 2 diabetes mellitus (T2DM). The primary objective of the study was to compare the immunogenicity of BGL-ASP and RMP; NovoRapid® in patient serum samples collected from phase-III clinical study. Immunogenicity was studied as the incidence of patients positive for anti-insulin Aspart (AIA) antibodies, developed against BGL-ASP/RMP at baseline, end of 12 week and end of 24 week of the treatment period. The changes in incidence of patients positive for AIA antibodies post-baseline were also studied to assess and compare the treatment-emergent antibody response (TEAR) between the treatment groups (BGL-ASP and RMP). Statistical evaluation was done by Fisher's exact test to compare the overall incidence of patients positive for AIA antibodies and the TEAR positives observed post-baseline in both the treated groups. An in-vitro neutralizing antibody assay (Nab assay) was also performed to study the effect of AIA antibodies in neutralizing the biological activity/metabolic function of the insulin. The neutralizing potential of AIA was studied by its effect on %glucose uptake. We also evaluated the association between AIA antibody levels and its impact on biological activity by studying the correlation between them.

RESULTS

Analysis of immunogenicity data suggested that the percentage of patients positive for AIA antibodies until week 24 was similar and comparable in both the treatment groups, BGL-ASP and RMP; NovoRapid®. The changes in incidence of patients positive for AIA post-baseline in terms of TEAR positives were also similar and comparable between the treatment groups. The results of the Nab assay with confirmed positive AIA samples from BGL-ASP- and RMP-treated groups did not have any negative impact on %glucose uptake by the cells in Nab assay, confirming the absence of neutralizing antibodies in both the treatment groups. The correlation studies also showed absence of association between AIA antibody levels and percentage glucose uptake in both BGL-ASP and RMP-NovoRapid® treatment groups. CONCLUSIONS: The immunogenicity assessment based on the overall incidence of patients positive for AIA, changes in incidence of patients positive for AIA post-baseline, TEAR rates and absence of neutralizing antibodies, were found to be apparently similar and comparable in both the treatment groups (BGL-ASP and RMP). We conclude from our studies that the immunogenicity of BGL-ASP is similar and comparable to RMP and the observed immunogenicity in terms of anti-insulin Aspart antibody levels had no impact on the biological activity of insulin.

Immunogenicity and safety of inactivated quadrivalent influenza vaccine compared with the trivalent vaccine for influenza infection: an overview of systematic reviews

BACKGROUND

Influenza infection is a highly preventable transmissible viral disease associated with mild upper respiratory symptoms and more severe conditions such as lethal pneumonia. Studies have shown that a broader spectrum influenza vaccine could reduce influenza's burden of disease in low- and middle-income countries. A considerable number of systematic reviews reported that quadrivalent influenza vaccines are considered more effective compared to trivalent vaccines, hence, there is a need for an overview in order to synthesize the current evidence pertaining to the comparison between quadrivalent and trivalent inactivated influenza vaccines.

OBJECTIVE

The aim was to summarize the evidence from systematic reviews that investigated the immunogenicity and safety of the Influenza's inactivated quadrivalent vaccine (QIV) compared to the trivalent vaccine (TIV), in the general population.

METHODS

We searched articles up to December 2022 at: Web of Science, EMBASE, MEDLINE, Cochrane Library, and SCOPUS. The search strategy was conducted following the PICO model. We included systematic reviews comparing the primary outcomes of immunogenicity (seroprotection rate and seroconversion rate) and adverse events using risk ratios. The AMSTAR 2 and ROBIS were used for quality assessments, and GRADE was used for evidence certainty assessments.

FINDINGS

We included five systematic reviews, totalling 47,740 participants. The Quadrivalent Inactivated Influenza Vaccine (QIV) exhibited enhanced immunogenicity in the context of B-lineage mismatch when compared to the Trivalent Inactivated Influenza Vaccine (TIV). While the safety profile of QIV was found to be comparable to that of TIV, the QIV showed a higher incidence of solicited local pain among children and adolescents, as well as an increased frequency of local adverse events within the adult population.

CONCLUSION

Our findings suggest that the QIV provides a superior immunogenicity response compared to the TIV in all age groups evaluated, especially when a lineage mismatch occurred. The safety of QIV was considered similar to the TIV, with no serious or systemic solicited or unsolicited adverse events; tough pain at the injection site was greater for QIV. We recommend caution owing to the high risk of bias in the selection process and no protocol registration.

Development of MDCK-based quadrivalent split seasonal influenza virus vaccine with high safety and immunoprotection: A preclinical study

Vaccination remains the best prevention strategy against influenza. The MDCK-based influenza vaccine prompted the development of innovative cell culture manufacturing processes. In the present study, we report the effects of multiple administrations of a candidate, seasonal, MDCK-based, quadrivalent split influenza virus vaccine MDCK-QIV in Sprague-Dawley (SD) rats. Moreover, the effects of the vaccine were evaluated in terms of fertility and early embryonic development, embryo-fetal development, and perinatal toxicity in the SD rats and immunogenicity in Wistar rats and BALB/c mice. Regarding the safety profile, MDCK-QIV demonstrated tolerance in local stimulation with repeated dose administration and presented no significant effect on the development, growth, behavior, fertility, and reproductive performance of the adult male rats, maternal rats, and their offspring. MDCK-QIV elicited strong hemagglutination inhibition neutralizing antibody response and protection against the influenza virus in the mouse model. Thus, data supported that MDCK-QIV could be further evaluated in human clinical trial, which is currently underway.

Impact of industry sponsorship on the quality of systematic reviews of vaccines: a cross-sectional analysis of studies published from 2016 to 2019

BACKGROUND

Systematic reviews (SRs) provide the highest level of evidence and inform evidence-based decision making in health care. Earlier studies found association with industry to be negatively associated with methodological quality of SRs. However, this has not been investigated in SRs on vaccines.

METHODS

We performed a systematic literature search using MEDLINE and EMBASE in March 2020. The results were restricted to those published between 2016 and 2019 with no language restrictions. Study characteristics were extracted by one person and checked by an experienced reviewer. The methodological quality of the SRs was assessed with the AMSTAR 2 tool by multiple reviewers after a calibration exercise was performed. A summary score for each SR was calculated. The Mann-Whitney U test and Fisher's exact test were performed to compare both groups.

RESULTS

Out of 185 SRs that met all inclusion criteria, 27 SRs were industry funded. Those were matched with 30 non-industry funded SRs resulting in a total sample size of 57. The mean AMSTAR 2 summary score across all SRs was 0.49. Overall, the median AMSTAR 2 summary score was higher for the non-industry funded SRs than for the industry-funded SRs (0.62 vs. 0.36; p < .00001). Lower ratings for industry funded SRs were consistent across all but one AMSTAR 2 item, though significantly lower only for three specific items.

CONCLUSION

The methodological quality of SRs in vaccination is comparable to SRs in other fields, while it is still suboptimal. We are not able to provide a satisfactory explanation why industry funded SRs had a lower methodological quality than non-industry funded SRs over recent years. Industry funding is an important indicator of methodological quality for vaccine SRs and should be carefully considered when appraising SR quality.

The safety and immunogenicity of a combined pertussis containing vaccine Tdap for HIV infected pregnant women and their newborns (WoMANPOWER) – A study protocol for a randomized clinical trial

Background: Globally there are an estimated 24.1 million cases and 160,700 deaths from pertussis annually in children under five years. The disease burden is higher in low- and middle-income countries, especially the African region, which contributes the largest proportions of cases and deaths. Immunization against pertussis in pregnancy is a recommended strategy for the prevention of infant pertussis in many high-income countries. However, vaccine immunogenicity and effectiveness may be different in immunocompromised individuals such as women living with HIV. There is a need to generate data on the impact of HIV infection in pregnancy on maternal and infant immunity to vaccines against pertussis. Methods: This is a phase II, randomized controlled observer blind clinical trial of 100 women living with HIV and 100 uninfected women randomized to either standard vaccines (tetanus diphtheria vaccine, Td) or a tetanus diphtheria-pertussis vaccine (Tdap). Participants aged 18-40 years carrying a low-risk singleton pregnancy with a gestational age between 16 and 26 weeks confirmed on ultrasound scan, with no history of receipt of tetanus or pertussis vaccines in the current pregnancy will be recruited. Women will receive either two doses of Td or a first dose of Td and second dose of Tdap vaccine. Participants will complete 14-day diary cards to monitor reactogenicity. Mother-infant dyads will be followed up until the infant is one year old. The outcomes include: safety for the pregnant woman and infant; anti-pertussis toxin (PT) and anti-filamentous haemagglutinin (FHA) IgG concentrations in maternal, cord and infant blood and breastmilk, compared by maternal HIV status. Discussion: This study will investigate whether vaccines given to women living with HIV have similar immunogenicity and reactogenicity to vaccines given to pregnant women without HIV and monitor the effect of Tdap in pregnancy on infant immune responses. clinicalTrials.gov registration: NCT04589312 (19/10/2020)

The Etiology of Pneumonia in HIV-uninfected South African Children: Findings From the Pneumonia Etiology Research for Child Health (PERCH) Study

BACKGROUND

Pneumonia is the major contributor to under 5 childhood mortality globally. We evaluated the etiology of pneumonia amongst HIV-uninfected South African children enrolled into the Pneumonia Etiology Research for Child Health case-control study.

METHODS

Cases, 1-59 months of age hospitalized with World Health Organization clinically defined severe/very severe pneumonia, were frequency-matched by age and season to community controls. Nasopharyngeal-oropharyngeal swabs were analyzed using polymerase chain reaction for 33 respiratory pathogens, and whole blood was tested for pneumococcal autolysin. Cases were also tested for Mycobacterium tuberculosis. Population etiologic fractions (EF) of pneumonia with radiologic evidence of consolidation/infiltrate were derived for each pathogen through Bayesian analysis.

RESULTS

Of the 805 HIV-uninfected cases enrolled based on clinical criteria, radiologically confirmed pneumonia was evident in 165 HIV-exposed, -uninfected, and 246 HIV-unexposed children. In HIV-exposed and HIV-unexposed children, respiratory syncytial virus was the most important pathogen with EFs of 31.6% [95% credible interval (CrI), 24.8%-38.8%] and 36.4% (95% CrI, 30.5%-43.1%), respectively. M. tuberculosis contributed EFs of 11.6% (95% CrI, 6.1%-18.8%) in HIV-exposed and 8.3% (95% CrI, 4.5%-13.8%) in HIV-unexposed children, including an EF of 16.3% (95% CrI, 6.1%-33.3%) in HIV-exposed children ≥12 months of age. Bacteremia (3.0% vs. 1.6%) and case fatality risk (3.6% vs. 3.7%) were similar in HIV-exposed and HIV-unexposed children.

CONCLUSIONS

Vaccination strategies targeting respiratory syncytial virus should be prioritized for prevention of pneumonia in children. Furthermore, interventions are required to address the high burden of tuberculosis in the pathogenesis of acute community-acquired pneumonia in settings such as ours.

A review on antiviral and immunomodulatory polysaccharides from Indian medicinal plants, which may be beneficial to COVID-19 infected patients

The emergence of the novel coronavirus, SARS-CoV-2 has pushed forward the world to experience the first pandemic of this century. Any specific drug against this RNA virus is yet to be discovered and presently, the COVID-19 infected patients are being treated symptomatically. During the last few decades, a number of polysaccharides with potential biological activities have been invented from Indian medicinal plants. Many polysaccharides, such as sulfated xylomannan, xylan, pectins, fucoidans, glucans, glucoarabinan, and arabinoxylan from Indian medicinal plants, have been shown to exhibit antiviral and immunomodulating activities. Plant polysaccharides exhibit antiviral activities through interference with the viral life cycle and inhibition of attachment of virus to host cell. Intake of certain immune stimulating plant polysaccharides may also protect from the virus to a certain extent. In process of continuous search for most potent drug, Indian plant polysaccharides may emerge as significant biomaterial to combat COVID-19. This review explores a number of polysaccharides from Indian medicinal plants which showed antiviral and immunomodulating activities. It is aimed to provide an overview about the composition, molecular mass, branching configuration and related bioactivities of polysaccharides which is crucial for their classification as possible drug to induce immune response in viral diseases.

Immunogenicity of seasonal inactivated influenza and inactivated polio vaccines among children in Senegal: Results from a cluster-randomized trial

Data on influenza vaccine immunogenicity in children are limited from tropical developing countries. We recently reported significant, moderate effectiveness of a trivalent inactivated influenza vaccine (IIV) in a controlled, cluster-randomized trial in children in rural Senegal during 2009, a year of H3N2 vaccine mismatch (NCT00893906). We report immunogenicity of IIV3 and inactivated polio vaccine (IPV) from that trial. We evaluated hemagglutination inhibition (HAI) and polio antibody titers in response to vaccination of three age groups (6 through 35 months, 3 through 5 years, and 6 through 8 years). As all children were IIV naïve, each received two vaccine doses, although titers were assessed after only the first dose for subjects aged 6 through 8 years. Seroconversion rates (4-fold titer rise or increase from <1:10 to ≥1:40) were 74-87% for A/H1N1, 76-87% for A/H3N2, and 54-79% for B/Yamagata. Seroprotection rates (HAI titer ≥ 1:40) were 79-88% for A/H1N1, 88-96% for A/H3N2, and 52-74% for B/Yamagata. IIV responses were lowest in the youngest age group, and they were comparable between ages 3 through 5 years after two doses and 6 through 8 years after one dose. We found that baseline seropositivity (HAI titer ≥ 1:10) was an effect modifier of IIV response. Using a seroprotective titer (HAI titer ≥ 1:160) recommended for IIV evaluation in children, we found that among subjects who were seropositive at baseline, 69% achieved seroprotection for both A/H1N1 and A/H3N2, while among those who were seronegative at baseline, seroprotection was achieved in 11% for A/H1N1 and 22% for A/H3N2. The IPV group had high baseline polio antibody seropositivity and appropriate responses to vaccination. Our data emphasize the importance of a two-dose IIV3 series in vaccine naïve children. IIV and IPV vaccines were immunogenic in Senegalese children.

Respiratory pathogen diversity and co-infections in rural Zambia

Objectives:

The role of respiratory co-infections in modulating disease severity remains understudied in southern Africa, particularly in rural areas. This study was performed to characterize the spectrum of respiratory pathogens in rural southern Zambia and the prognostic impact of co-infections.

Methods:

Respiratory specimens collected from inpatient and outpatient participants in a viral surveillance program in 2018–2019 were tested for selected viruses and a typical bacteria using the Xpert Xpress Flu/RSV assay and FilmArray Respiratory Panel EZ. Participants were followed for 3–5 weeks to assess their clinical course. Multivariable regression was used to examine the role of co-infections in influencing disease severity.

Results:

A respiratory pathogen was detected in 63.2% of samples from 671 participants who presented with influenza-like illness. Common pathogens identified included influenza virus (18.2% of samples), respiratory syncytial virus (RSV) (11.8%), rhinovirus (26.4%), and coronavirus (6.0%). Overall, 6.4% of participants were co-infected with multiple respiratory pathogens. Compared to mono-infections, co-infections were found not to be associated with severe clinical illness either overall (relative risk (RR) 0.72, 95% confidence interval (CI) 0.39–1.32) or specifically with influenza virus (RR 0.80, 95% CI 0.14–4.46) or RSV infections (RR 0.44, 95% CI 0.17–1.11).

Conclusions:

Respiratory infections in rural southern Zambia were associated with a wide range of viruses. Respiratory co-infections in this population were not associated with clinical severity.

Occurrence and possible roles of polysaccharides in fungi and their influence on the development of new technologies

The article summarizes the roles of polysaccharides in the biology of fungi and their relationship in the development of new technologies. The comparative approach between the evolution of fungi and the chemistry of glycobiology elucidated relevant aspects about the role of polysaccharides in fungi. Also, based on the knowledge of fungal glycobiology, it was possible to address the development of new technologies, such as the production of new anti-tumor drugs, vaccines, biomaterials, and applications in the field of robotics. We conclude that polysaccharides activate pathways of apoptosis, secretion of pro-inflammatory substances, and macrophage, inducing anticancer activity. Also, the activation of the immune system, which opens the way for the production of vaccines. The development of biomaterials and parts for robotics is a promising and little-explored field. Finally, the article is multidisciplinary, with a different and integrated approach to the role of nature in the sustainable development of new technologies.

Impact of Helminth Infections during Pregnancy on Vaccine Immunogenicity in Gabonese Infants

Helminth infections are common in sub-Saharan Africa. Besides direct clinical effects, a bias towards a T helper type 2 (Th2) cell immune response is observed. The consequences of parasite infection during pregnancy for the mother and particularly for the fetus and the newborn can be severe and may include impaired immune response during acute infection and vaccination. Here, we present data of immune responses to vaccines given within the expanded program on immunization (EPI) of infants born to helminth infected or non-infected mothers. The study was conducted in Lambaréné and surroundings, Gabon. Maternal helminth infection was diagnosed microscopically using the Kato-Katz method for soil-transmitted helminths (STH), urine filtration for Schistosoma haematobium infections and the saponin-based method for filarial infections. Plasma antibody levels to different vaccine antigens were measured in mothers and their offspring by enzyme-linked immunosorbent assay (ELISA) at different timepoints. We found 42.3% of the mothers to be infected with at least one helminth species. Significantly lower anti-tetanus toxoid immunoglobulin (Ig) G was detected in the cord blood of infants born to helminth infected mothers. Following vaccination, immune responses of the infants to EPI vaccines were similar between the two groups at nine and 12 months. Even though infection with helminths is still common in pregnant women in Gabon, in our setting, there was no evidence seen for a substantial effect on infants’ immune responses to vaccines given as part of the EPI.

A Devil of a Transmissible Cancer

Devil facial tumor disease (DFTD) encompasses two independent transmissible cancers that have killed the majority of Tasmanian devils. The cancer cells are derived from Schwann cells and are spread between devils during biting, a common behavior during the mating season. The Centers for Disease Control and Prevention (CDC) defines a parasite as "An organism that lives on or in a host organism and gets its food from, or at, the expense of its host." Most cancers, including DFTD, live within a host organism and derive resources from its host, and consequently have parasitic-like features. Devil facial tumor disease is a transmissible cancer and, therefore, DFTD shares one additional feature common to most parasites. Through direct contact between devils, DFTD has spread throughout the devil population. However, unlike many parasites, the DFTD cancer cells have a simple lifecycle and do not have either independent, vector-borne, or quiescent phases. To facilitate a description of devil facial tumor disease, this review uses life cycles of parasites as an analogy.

Effect of a Russian-backbone live-attenuated influenza vaccine with an updated pandemic H1N1 strain on shedding and immunogenicity among children in The Gambia: an open-label, observational, phase 4 study

BACKGROUND

The efficacy and effectiveness of the pandemic H1N1 (pH1N1) component in live attenuated influenza vaccine (LAIV) is poor. The reasons for this paucity are unclear but could be due to impaired replicative fitness of pH1N1 A/California/07/2009-like (Cal09) strains. We assessed whether an updated pH1N1 strain in the Russian-backbone trivalent LAIV resulted in greater shedding and immunogenicity compared with LAIV with Cal09.

METHODS

We did an open-label, prospective, observational, phase 4 study in Sukuta, a periurban area in The Gambia. We enrolled children aged 24-59 months who were clinically well. Children received one dose of the WHO prequalified Russian-backbone trivalent LAIV containing either A/17/California/2009/38 (Cal09) or A/17/New York/15/5364 (NY15) based on their year of enrolment. Primary outcomes were the percentage of children with LAIV strain shedding at day 2 and day 7, haemagglutinin inhibition seroconversion, and an increase in influenza haemagglutinin-specific IgA and T-cell responses at day 21 after LAIV. This study is nested within a randomised controlled trial investigating LAIV-microbiome interactions (NCT02972957).

FINDINGS

Between Feb 8, 2017, and April 12, 2017, 118 children were enrolled and received one dose of the Cal09 LAIV from 2016-17. Between Jan 15, 2018, and March 28, 2018, a separate cohort of 135 children were enrolled and received one dose of the NY15 LAIV from 2017-18, of whom 126 children completed the study. Cal09 showed impaired pH1N1 nasopharyngeal shedding (16 of 118 children [14%, 95% CI 8·0-21·1] with shedding at day 2 after administration of LAIV) compared with H3N2 (54 of 118 [46%, 36·6-55·2]; p<0·0001) and influenza B (95 of 118 [81%, 72·2-87·2]; p<0·0001), along with suboptimal serum antibody (seroconversion in six of 118 [5%, 1·9-10·7]) and T-cell responses (CD4+ interferon γ-positive and/or CD4+ interleukin 2-positive responses in 45 of 111 [41%, 31·3-50·3]). After the switch to NY15, a significant increase in pH1N1 shedding was seen (80 of 126 children [63%, 95% CI 54·4-71·9]; p<0·0001 compared with Cal09), along with improvements in seroconversion (24 of 126 [19%, 13·2-26·8]; p=0·011) and influenza-specific CD4+ T-cell responses (73 of 111 [66%, 60·0-75·6; p=0·00028]). The improvement in pH1N1 seroconversion with NY15 was even greater in children who were seronegative at baseline (24 of 64 children [38%, 95% CI 26·7-49·8] vs six of 79 children with Cal09 [8%, 2·8-15·8]; p<0·0001). Persistent shedding to day 7 was independently associated with both seroconversion (odds ratio 12·69, 95% CI 4·1-43·6; p<0·0001) and CD4+ T-cell responses (odds ratio 7·83, 95% CI 2·99-23·5; p<0·0001) by multivariable logistic regression.

INTERPRETATION

The pH1N1 component switch that took place between 2016 and 2018 might have overcome the poor efficacy and effectiveness reported with previous LAIV formulations. LAIV effectiveness against pH1N1 should, therefore, improve in upcoming influenza seasons. Our data highlight the importance of assessing replicative fitness, in addition to antigenicity, when selecting annual LAIV components.

FUNDING

The Wellcome Trust.