Efficacy of the COVID-19 vaccination in patients with asymptomatic or mild illness during the Omicron epidemic in Guangzhou: a multi-centre retrospective cohort study

BACKGROUND

Despite the widespread administration of coronavirus disease 2019 (COVID-19) vaccines, the impact on patients with asymptomatic to mild illness remains unclear. Here, we aimed to assess the efficacy of various vaccine doses and types on the duration of isolation duration and discharge rates, the viral shedding duration, and negative rates in asymptomatic to mild COVID-19 patients.

METHODS

We included adult patients at the Fangcang isolation centres in Pazhou or Yongning between November and December 2022. We analysed data on basic demographics, admission details, laboratory indicators and vaccination information.

RESULTS

A total of 6560 infected patients were included (3584 from Pazhou and 2976 from Yongning). Of these, 90.6% received inactivated vaccines, 3.66% received recombinant SARS-CoV-2 spike protein subunit vaccines and 0.91% received adenovirus vaccines. Among the 6173 vaccinated individuals, 71.9% received a booster dose. By day 9, the isolation rate reached 50% among vaccinated patients. On day 7.5, the positive rate among vaccinated individuals reached 50%.

CONCLUSIONS

Full vaccination was effective, with heterologous vaccines showing greater efficacy than inactivated vaccines alone. However, there was no significant difference in the vaccine protective effect 12 months after vaccination.

Evolution of H7N9 highly pathogenic avian influenza virus in the context of vaccination

Human infections with the H7N9 influenza virus have been eliminated in China through vaccination of poultry; however, the H7N9 virus has not yet been eradicated from poultry. Carefully analysis of H7N9 viruses in poultry that have sub-optimal immunity may provide a unique opportunity to witness the evolution of highly pathogenic avian influenza virus in the context of vaccination. Between January 2020 and June 2023, we isolated 16 H7N9 viruses from samples we collected during surveillance and samples that were sent to us for disease diagnosis. Genetic analysis indicated that these viruses belonged to a single genotype previously detected in poultry. Antigenic analysis indicated that 12 of the 16 viruses were antigenically close to the H7-Re4 vaccine virus that has been used since January 2022, and the other four viruses showed reduced reactivity with the vaccine. Animal studies indicated that all 16 viruses were nonlethal in mice, and four of six viruses showed reduced virulence in chickens upon intranasally inoculation. Importantly, the H7N9 viruses detected in this study exclusively bound to the avian-type receptors, having lost the capacity to bind to human-type receptors. Our study shows that vaccination slows the evolution of H7N9 virus by preventing its reassortment with other viruses and eliminates a harmful characteristic of H7N9 virus, namely its ability to bind to human-type receptors.

Stakeholders' perspectives on barriers to and facilitators of school-based HPV vaccination in the context of COVID-19 pandemic-related disruption: a qualitative mixed methods study

Despite successfully implementing the Human Papilloma Virus Vaccine (HPVV) program, Saskatchewan (SK) struggled to improve HPVV uptake rates. This suboptimal uptake of HPVV with a status quo of HPV-linked cervical cancer incidence rate is mainly because HPVV's impact on cancer prevention has not been realized adequately by vaccine providers and receivers. Further exploration of determinants of HPVV uptake is required to uncover high-resolution quality improvement targets for investment and situate contextually appropriate policies to improve its uptake. The study undertook a qualitative inquiry into understanding stakeholders' perspectives on HPVV experience through school-based programmes. It collected data through semi-structured initial interviews (N = 16) and follow-up interviews (N = 10) from across Saskatchewan's four Integrated Service Areas. Document analysis was conducted on all publicly available documents that included information on HPVV from January 2015 to July 2023. Thematic analysis of the data identified that inadequate information, awareness and education about HPV infection and HPVV among several groups, especially, parents, youth and school staff, was the main barrier to optimal HPVV uptake. Vaccine-related logistics, including the technical and text-heavy vaccine information sheet, understaffing, and time constraints, were other important factors that impeded HPVV uptake. A person-centred approach could educate parents in multiple dimensions.

Levels of antibodies against the monkeypox virus compared by HIV status and historical smallpox vaccinations: a serological study

Men who have sex with men and people living with HIV are disproportionately affected in the 2022 multi-country monkeypox epidemic. The smallpox vaccine can induce cross-reactive antibodies against the monkeypox virus (MPXV) and reduce the risk of infection. Data on antibodies against MPXV induced by historic smallpox vaccination in people with HIV are scarce. In this observational study, plasma samples were collected from people living with and without HIV in Shenzhen, China. We measured antibodies binding to two representative proteins of vaccinia virus (VACV; A27L and A33R) and homologous proteins of MPXV (A29L and A35R) using an enzyme-linked immunosorbent assay. We compared the levels of these antibodies between people living with and without HIV. Stratified analyses were performed based on the year of birth of 1981 when the smallpox vaccination was stopped in China. Plasma samples from 677 people living with HIV and 746 people without HIV were tested. A consistent pattern was identified among the four antibodies, regardless of HIV status. VACV antigen-reactive and MPXV antigen-reactive antibodies induced by historic smallpox vaccination were detectable in the people born before 1981, and antibody levels reached a nadir during or after 1981. The levels of smallpox vaccine-induced antibodies were comparable between people living with HIV and those without HIV. Our findings suggest that the antibody levels against MPXV decreased in both people living with and without HIV due to the cessation of smallpox vaccination.

Mucosal and systemic immune correlates of viral control after SARS-CoV-2 infection challenge in seronegative adults

Human infection challenge permits in-depth, early, and pre-symptomatic characterization of the immune response, enabling the identification of factors that are important for viral clearance. Here, we performed intranasal inoculation of 34 young adult, seronegative volunteers with a pre-Alpha severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strain. Of these participants, 18 (53%) became infected and showed an interferon-dominated mediator response with divergent kinetics between nasal and systemic sites. Peripheral CD4+ and CD8+ T cell activation and proliferation were early and robust but showed distinct kinetic and phenotypic profiles; antigen-specific T cells were largely CD38+Ki67+ and displayed central and effector memory phenotypes. Both mucosal and systemic antibodies became detectable around day 10, but nasal antibodies plateaued after day 14 while circulating antibodies continued to rise. Intensively granular measurements in nasal mucosa and blood allowed modeling of immune responses to primary SARS-CoV-2 infection that revealed CD8+ T cell responses and early mucosal IgA responses strongly associated with viral control, indicating that these mechanisms should be targeted for transmission-reducing intervention.

Immunogenicity and safety of COVID-19 booster vaccination: A population-based clinical trial to identify the best vaccination strategy

BACKGROUND

Various SARS-CoV-2 variants of concerns (VOCs) characterized by higher transmissibility and immune evasion have emerged. Despite reduced vaccine efficacy against VOCs, currently available vaccines provide protection. Population-based evidence on the humoral immune response after booster vaccination is crucial to guide future vaccination strategies and in preparation for imminent COVID-19 waves.

METHODS

This multicenter, population-based cohort study included 4697 individuals ≥18 years of age who received a booster vaccination. Antibody levels against SARS-CoV-2 receptor binding domain (RBD) and neutralizing antibodies against wild-type (WT) virus and Omicron variants were assessed at baseline (day of booster vaccination) and after four weeks. Safety was evaluated daily within the first week using a participant-completed electronic diary. Antibody levels were compared across different vaccination strategies, taking into account individual host factors.

RESULTS

Our main model including 3838 participants revealed that individuals who received a booster with mRNA-1273 compared to BNT162b2 vaccine had a significantly higher increase (95 %CI) in anti-RBD-antibody levels (37,707 BAU/mL [34,575-40,839] vs. 27,176 BAU/mL [26,265-28,087]), and of neutralization levels against WT (1,681 [1490-1872] vs. 1141 [1004-1278] and Omicron variant (422 [369-474] vs. 329 [284-374]). Neutralizing antibody titres highly correlated with anti-RBD antibodies, with neutralizing capacity 4.4 fold higher against WT compared to Omicron. No differences in safety were found between the two booster vaccines.

CONCLUSION

Our study underlines the superiority of a booster vaccination with mRNA-1273, independent of the primary vaccination and therefore provides guidance on the vaccination strategy.

Shedding of measles vaccine RNA in children after receiving measles, mumps and rubella vaccination

BACKGROUND

Measles, mumps, and rubella(MMR) vaccination is critical to measles outbreak responses. However, vaccine reactions and detection of measles vaccine RNA in recently immunized persons may complicate case classification especially in those presenting with another respiratory viral illness. We aim to characterize cases of measles vaccine shedding in recently vaccinated children presenting with respiratory viral symptoms.

METHODS

Children who were tested with a multiplex respiratory panel <30 days after receiving MMR were identified. Remnant nasopharyngeal(NP) samples were tested for measles vaccine by PCR. Medical records were reviewed for demographics, presenting symptoms, and test results.

RESULTS

From January 2022 to March 2023, 127 NP from children who received MMR were tested. Ninety-six NP were collected after the first dose, of which 33(34.4 %) were positive for vaccine RNA. The median interval between MMR and detection was 11.0 days. Thirty-one NP were collected after the second MMR and 1(3.2 %) was positive; time between the vaccination and detection was 18.9 days. Median cycle threshold(Ct) value of the measles PCR for vaccine shedding was significantly higher than median Ct in children with wild-type infection.

CONCLUSION

Shedding of measles vaccine RNA is not uncommon and vaccine RNA can be detected up to 29 days post MMR; the amount of vaccine RNA shedding is low indicated by high Ct values. Clinicians and public health officials should consider performing measles vaccine testing on those testing positive for measles within one month of MMR vaccination, especially if the Ct value is high and definitive epidemiological links are absent.

SARS-CoV-2 mRNA vaccination and short-term changes in viral load and CD4/CD8 T-cell counts in people living with HIV

OBJECTIVES

To investigate whether SARS-CoV-2 messenger RNA (mRNA) vaccination has an impact on HIV-related viro-immunological parameters.

METHODS

People with HIV (PWH) in the VAXICONA-ORCHESTRA cohort who received one or more doses of SARS-CoV-2 mRNA vaccine and for whom paired measures of immuno-virological markers (viral load, clusters of differentiation [CD]4, and CD8 count 1 month before and after a vaccine dose [VD]) were available were included. Paired t-test and generalized estimating equation linear regression analyses were used to study changes over ± 1 month around the VD. Subgroup analyses were performed.

RESULTS

A total of 510 PWH were enrolled: the median age was 55 years (interquartile range 46-60 years), the CD4 and CD8 count were 489 (287-719) and 790 (59-1104) cells/mm3, respectively, and 81% received three VDs. After a median of 28 (3-53) days from VD, CD4 count increased by +15 cells/mm3 (SD ± 129.7, P = 0.001) and CD8 by +12 (±250.5, P = 0.199) and the viral load decreased by -0.11 log10 (±0.88, P = 0.001). Similar results were observed after restricting the analysis to viro-suppressed PWH, with CD4 ≤200/mm3, more than 6 months of antiretroviral therapy before VD and after excluding previous COVID-19.

CONCLUSIONS

A small significant increase in CD4 count and a negligible drop in HIV RNA were observed. Our findings are consistent with the hypothesis that SARS-CoV-2 mRNA vaccine can prime CD4 T spike-specific cells, even in the more immuno-compromised PWH.

Risk of Corneal Graft Rejection and Vaccination: A Matched Case-Control Study From a United States Integrated Health Care System

PURPOSE

Data on vaccine-associated corneal transplant rejections are limited. We examined the association between graft rejection and vaccination.

DESIGN

Matched case-control METHODS: We used electronic health records to identify corneal transplant recipients between January 2008 and August 2022 at Kaiser Permanente Southern California. Cases were transplant recipients who experienced a graft rejection (outcome) during the study period. Randomly selected controls who did not experience a corneal graft rejection at their matched cases' index date (rejection date) were matched in a 3:1 ratio to cases. For controls, index date was determined by adding the number of days between transplant and graft rejection of their matched case to the control's transplant date.

RESULTS

The study included 601 cases and 1803 matched controls (mean age 66 years [s.d. 17.0], 52% female, 47% non-Hispanic white). Twenty-three% of cases and 22% of controls received ≥1 vaccinations within 12 weeks prior to the index date. The adjusted odds ratio (aOR) for vaccination in the 12 weeks prior to index date, comparing cases to controls was 1.17 (95% CI: 0.91, 1.50]). The aOR was 1.09 (0.84, 1.43) for 1 vaccination, 1.53 (0.90, 2.61) for 2 vaccinations, and 1.79 (0.55, 5.57) for ≥3 vaccinations. The aOR was 1.60 (0.81, 3.14) for mRNA vaccines, and 1.19 (0.80, 1.78) for adjuvanted/high dose vaccines.

CONCLUSIONS

We found no evidence to suggest an association between vaccination and graft rejection. Our findings provide support for the completion of recommended vaccinations for corneal transplant recipients, without significantly increasing the risk of graft rejection.

Maternal singing reduced pain indexes in 2-month-old infants and increased proximity during vaccinations

AIM

Immunisation is a global health priority, but methods of non-pharmacological pain relief are not widely used in routine clinical practice. In this study, we set out to investigate the effects of maternal singing during the routine vaccination of infants.

METHODS

We recruited 67 mother-infant pairs at Health Centres in the Aosta Region of Italy. Infants aged 2-4 months were randomly allocated to a singing intervention group or to a control group whose injections were administered following standard practice. Pre- and post-immunisation pain was blindly assessed using the Modified Behavioural Pain Scale, and mother-infant proximity indexes were assigned based on muted video-tracks.

RESULTS

When assessed for pain, the infants in the maternal singing group were assigned significantly lower movement indexes (p = 0.032) and marginally significantly lower cry indexes (p = 0.076). A higher frequency of mother-to-infant gaze (p < 0.005) was observed in the singing group dyads. Finally, the intervention group mothers' self-perceived ease in singing was correlated with their previous singing experience and with lower anxiety following the vaccination procedure (p < 0.05).

CONCLUSION

Maternal singing during immunisation procedures benefits both mothers and babies. The practice of singing is a biologically rooted and adaptive form of intuitive parental communication that should be encouraged, especially in at-risk populations.

Transplacental transfer of maternal antibodies following immunization with recombinant pertussis vaccines during pregnancy: Real-world evidence

AIM/OBJECTIVE

This study investigates placental antibody transfer following recombinant pertussis vaccination in pregnancy in a real-world setting.

METHODS

This postmarketing observational study recruited pregnant women vaccinated with monovalent recombinant acellular pertussis (aP) vaccine (aPgen; n = 199) or combined to tetanus-diphtheria (TdaPgen; n = 200), or Td-vaccine only (n = 54). Pregnancy, delivery, and neonatal outcomes were assessed. Cord blood was collected postdelivery and pertussis toxin (PT)-IgG, filamentous hemagglutinin (FHA)-IgG, and PT-neutralizing antibodies (PT-Nab) were assessed.

RESULTS

No adverse pregnancy, delivery, or neonatal outcomes attributed to aPgen, TdaPgen, or Td vaccination were reported. High anti-PT antibody levels were detected in cord samples from women vaccinated with aPgen (geometric mean concentration [GMC] PT-IgG 206.1 IU/ml, 95% confidence intervals [CI]: 164.3-258.6; geometric mean titer [GMT] PT-Nab 105.3 IU/ml, 95% CI: 81.7-135.8) or TdaPgen (GMC PT-IgG 153.1 IU/ml, 95% CI: 129.1-181.5; GMT PT-Nab 81.5 IU/ml, 95% CI: 66.4-100.0). In the Td-only group, anti-PT antibodies were low (GMC PT-IgG 6.5 IU/ml, 95% CI: 4.9-8.8; GMT PT-Nab 3.8 IU/ml, 95% CI: 2.8-5.1). The same was found for FHA-IgG. Recombinant pertussis vaccination at <27 or 27-36 weeks gestation induced similar cord pertussis antibody levels.

CONCLUSION

This first real-world study confirms that recombinant pertussis vaccination in the second or third trimester of pregnancy results in high levels of passive immunity in infants. Thai Clinical Trial Registry: TCTR20200528006.

Orthopox viruses: is the threat growing?

BACKGROUND

Smallpox was a major cause of human mortality until its eradication, but the threat of orthopox viruses has not disappeared. Since the eradication of smallpox and the cessation of the related vaccination campaigns, the threat has been growing, as evidenced by the currently ongoing worldwide Mpox outbreak. In addition to threats of an evolving Mpox, we must also be aware of a myriad of other threats that remain. Many countries still lack biosecurity regulations reflecting the recent technological advances, and the threat of bioterrorism remains ever present. Reconstruction of smallpox is a distinct possibility, as are other scenarios whereby other orthopox viruses may be made more fit for transmission in humans.

OBJECTIVES

To outline and discuss potential biosafety and biosecurity threats posed by orthopox viruses.

SOURCES

Published scientific literature, news articles, and international agreements.

CONTENT AND IMPLICATIONS

It would be wise to take steps to mitigate these threats now. Vaccination campaigns should be considered in areas with frequent orthopox outbreaks, and more efforts must be made to put a final end to the Mpox outbreak. In many countries, national biosafety and biosecurity regulations may need to be revised and strengthened to better reflect the threats posed by new technologies, including controls on synthesis of smallpox sequences. Furthermore, more international cooperation and aid is needed. The present global Mpox outbreak could likely have been prevented had areas where Mpox is endemic not been neglected. Future outbreaks could be much worse.

Improvement of quality of care provided to outpatients with hepatic cirrhosis after an educational intervention

OBJECTIVE

A set of indicators has been reported to measure the quality of care for cirrhotic patients, and previously published studies report variable adherence rates to these indicators. This study aimed to assess the quality of care provided to cirrhotic outpatients before and after an educational intervention by determining its impact on adherence to quality indicators.

METHODS

We conducted a quasi-experimental, cross-sectional study including 324 cirrhotic patients seen in 2017 and 2019 at a tertiary teaching hospital in Spain. Quality indicators were assessed in five domains: documentation of cirrhosis etiology, disease severity assessment, hepatocellular carcinoma (HCC) screening, variceal bleeding prophylaxis, and vaccination. After identifying areas for improvement, an educational intervention was implemented. A second evaluation was performed after the intervention to assess changes in adherence rates.

RESULTS

Before the intervention, adherence rates were excellent (>90%) for indicators related to variceal bleeding prophylaxis and documentation of cirrhosis etiology, acceptable (60-80%) for HCC screening and disease severity assessment, and poor (<50%) for vaccinations. After the educational intervention, there was a statistically significant improvement in adherence rates for eight indicators related to HCC screening (70-90%), disease severity assessment (90%), variceal bleeding prophylaxis (>90%), and vaccinations (60-90%).

CONCLUSION

Our study demonstrates a significant improvement in the quality of care provided to cirrhotic outpatients after an educational intervention. The findings highlight the importance of targeted educational interventions to enhance adherence to quality indicators in the management of cirrhosis.

Age-specific prevalence of IgG against measles/rubella and the impact of routine and supplementary immunization activities: A multistage random cluster sampling study with mathematical modelling

BACKGROUND

Vietnam continues to have measles and rubella outbreaks following supplementary immunization activities (SIA) and routine immunization despite both having high reported coverage. To evaluate immunization activities, age-specific immunity against measles and rubella, and the number of averted Congenital Rubella Syndrome (CRS) cases, must be estimated.

METHODS

Dried blood spots were collected from 2091 randomly selected individuals aged 1-39 years. Measles and rubella virus-specific immunoglobulin G (IgG) were measured by enzyme immunoassay. Results were considered positive at ≥120 mIU/mL for measles and ≥10 IU/mL for rubella. The number of CRS cases averted by immunization since 2014 were estimated using mathematical modelling.

RESULTS

Overall IgG seroprevalence was 99.7% (95%CI: 99.2-99.9) for measles and 83.6% (95%CI: 79.3-87.1) for rubella. Rubella IgG seroprevalence was higher among age groups targeted in the SIA than in non-targeted young adults (95.4% [95%CI: 92.9-97.0] vs 72.4% [95%CI: 63.1-80.1]; P < 0.001). The estimated number of CRS cases averted in 2019 by immunization activities since 2014 ranged from 126 (95%CI: 0-460) to 883 (95%CI: 0-2271) depending on the assumed postvaccination reduction in the force of infection.

CONCLUSIONS

The results suggest the SIA was effective, while young adults born before 1998 who remain unprotected for rubella require further vaccination.

Effects of COVID-19 mRNA vaccination on HIV viremia and reservoir size

OBJECTIVE

The immunogenic nature of coronavirus disease 2019 (COVID-19) mRNA vaccines led to some initial concern that these could stimulate the HIV reservoir. We analyzed changes in plasma HIV loads (pVL) and reservoir size following COVID-19 mRNA vaccination in 62 people with HIV (PWH) receiving antiretroviral therapy (ART), and analyzed province-wide trends in pVL before and after the mass vaccination campaign.

DESIGN

Longitudinal observational cohort and province-wide analysis.

METHODS

Sixty-two participants were sampled prevaccination, and one month after their first and second COVID-19 immunizations. Vaccine-induced anti-SARS-CoV-2-Spike antibodies in serum were measured using the Roche Elecsys Anti-S assay. HIV reservoirs were quantified using the intact proviral DNA assay; pVL were measured using the cobas 6800 (lower limit of quantification: 20 copies/ml). The province-wide analysis included all 290 401 pVL performed in British Columbia, Canada between 2012 and 2022.

RESULTS

Prevaccination, the median intact reservoir size was 77 [interquartile range (IQR): 20-204] HIV copies/million CD4 + T-cells, compared to 74 (IQR: 27-212) and 65 (IQR: 22-174) postfirst and -second dose, respectively (all comparisons P > 0.07). Prevaccination, 82% of participants had pVL <20 copies/ml (max: 110 copies/ml), compared to 79% postfirst dose (max: 183 copies/ml) and 85% postsecond dose (max: 79 copies/ml) ( P  > 0.4). There was no evidence that the magnitude of the vaccine-elicited anti-SARS-CoV-2-Spike immune response influenced pVL nor changes in reservoir size ( P  > 0.6). We found no evidence linking the COVID-19 mass vaccination campaign to population-level increases in detectable pVL frequency among all PWH in the province, nor among those who maintained pVL suppression on ART.

CONCLUSION

We found no evidence that COVID-19 mRNA vaccines induced changes in HIV reservoir size nor plasma viremia.

The contributions of vaccination and natural infection to the production of neutralizing antibodies against the SARS-CoV-2 prototype strain and variants

OBJECTIVES

To evaluate the neutralizing antibody (NAb) levels against the SARS-CoV-2 Omicron variants BF.7, BQ.1, BQ.1.1, XBB.1, and XBB.1.5 after vaccination and natural infection.

METHODS

The NAbs against the different viral strains of 490 individuals with SARS-CoV-2 and 187 without SARS-CoV-2 in the Beijing COVID-19 outbreak during December 2022 to January 2023 were analyzed.

RESULTS

In uninfected individuals, limited levels of NAbs were produced against the prototype and variant strains after two doses vaccine but significantly increased after three or four doses of the vaccine. The infected individuals had high NAbs levels against the BF.7, BQ.1, and BQ.1.1 variants and moderate NAbs levels against the XBB.1 and XBB.1.5 variants. The highest NAbs levels were observed after two inoculation doses. The third and fourth doses vaccine did not result in a significant increase the NAbs levels. After the last dose of vaccination, the NAbs levels peaked at 12 months for the prototype and BF.7 and between 6 to 12 months for the BQ.1, BQ.1.1, XBB.1, and XBB.1.5 variants.

CONCLUSIONS

The immune response decreases as the virus mutates. If booster vaccination is considered necessary, it is suggested for at least 6 months after infection.

SIRS epidemics with individual heterogeneity of immunity waning

In the current paper we analyse an extended SIRS epidemic model in which immunity at the individual level wanes gradually at exponential rate, but where the waning rate may differ between individuals, for instance as an effect of differences in immune systems. The model also includes vaccination schemes aimed to reach and maintain herd immunity. We consider both the informed situation where the individual waning parameters are known, thus allowing selection of vaccinees being based on both time since last vaccination as well as on the individual waning rate, and the more likely uninformed situation where individual waning parameters are unobserved, thus only allowing vaccination schemes to depend on time since last vaccination. The optimal vaccination policies for both the informed and uniformed heterogeneous situation are derived and compared with the homogeneous waning model (meaning all individuals have the same immunity waning rate), as well as to the classic SIRS model where immunity at the individual level drops from complete immunity to complete susceptibility in one leap. It is shown that the classic SIRS model requires least vaccines, followed by the SIRS with homogeneous gradual waning, followed by the informed situation for the model with heterogeneous gradual waning. The situation requiring most vaccines for herd immunity is the most likely scenario, that immunity wanes gradually with unobserved individual heterogeneity. For parameter values chosen to mimic COVID-19 and assuming perfect initial immunity and cumulative immunity of 12 months, the classic homogeneous SIRS epidemic suggests that vaccinating individuals every 15 months is sufficient to reach and maintain herd immunity, whereas the uninformed case for exponential waning with rate heterogeneity corresponding to a coefficient of variation being 0.5, requires that individuals instead need to be vaccinated every 4.4 months.

Efficacy and immunogenicity of AS04-HPV-16/18 vaccine in females with existing cervical HR-HPV infection at first vaccination: A pooled analysis of four large clinical trials worldwide

Females with existing high-risk HPV (HR-HPV) infections remain at risk of subsequent multiple or recurrent infections, on which benefit from HPV vaccines was under-reported. We pooled individual-level data from four large-scale, RCTs of AS04-HPV-16/18 vaccine to evaluate efficacy and immunogenicity in females DNA-positive to any HR-HPV types at first vaccination. Females receiving the AS04-HPV-16/18 vaccine in the original RCTs constituted the vaccine group in the present study, while those unvaccinated served as the control group. Vaccine efficacy (VE) against new infections and associated cervical intraepithelial neoplasia (CIN) 2+ in females DNA-negative to the considered HR-HPV type but positive to any other HR-HPV types, VE against reinfections in females DNA-positive to the considered HR-HPV type but cleared naturally during later follow-up, and levels of anti-HPV-16/18 IgG were assessed. Our final analyses included 5137 females (vaccine group = 2532, control group = 2605). The median follow-up time was 47.88 months (IQR: 45.72-50.04). For the prevention of precancerous lesions related to the non-infected HR-HPV types at baseline, VE against HPV-16/18 related CIN 2+ was 82.70% (95% CI: 63.70-93.00%). For the prevention of reinfections related to the infected HR-HPV types following natural clearance, VE against HPV-16/18 12MPI was non-significant (p > .05), albeit robust immunity persisted for at least 48 months. Females with existing HR-HPV infections at first vaccination still benefit from vaccination in preventing precancers related to the non-infected types at baseline. VE against reinfections related to the infected types following natural clearance remains to be further investigated.

Mucosal vaccination in a murine gnotobiotic model of Giardia lamblia infection

Giardia lamblia is an important protozoan cause of diarrheal disease worldwide, delayed development and cognitive impairment in children in low- and middle-income countries, and protracted post-infectious syndromes in developed regions. G. lamblia resides in the lumen and at the epithelial surface of the proximal small intestine but is not mucosa invasive. The protozoan parasite is genetically diverse with significant genome differences across strains and assemblages. Animal models, particularly murine models, have been instrumental in defining mechanisms of host defense against G. lamblia, but mice cannot be readily infected with most human pathogenic strains. Antibiotic pretreatment can increase susceptibility, suggesting that the normal microbiota plays a role in controlling G. lamblia infection in mice, but the broader implications on susceptibility to diverse strains are not known. Here, we have used gnotobiotic mice to demonstrate that robust intestinal infection can be achieved for a broad set of human-pathogenic strains of the genetic assemblages A and B. Furthermore, gnotobiotic mice were able to eradicate infection with a similar kinetics to conventional mice after trophozoite challenge. Germ-free mice could also be effectively immunized by the mucosal route with a protective antigen, α1-giardin, in a manner dependent on CD4 T cells. These results indicate that the gnotobiotic mouse model is powerful for investigating acquired host defenses in giardiasis, as the mice are broadly susceptible to diverse G. lamblia strains yet display no apparent defects in mucosal immunity needed for controlling and eradicating this lumen-dwelling pathogen.

Lower Humoral and Cellular Immunity Following Asymptomatic SARS-CoV-2 Infection Compared to Symptomatic Infection in Education (The ACE Cohort)

PURPOSE

Asymptomatic SARS-CoV-2 infections were widely reported during the COVID-19 pandemic, acting as a hidden source of infection. Many existing studies investigating asymptomatic immunity failed to recruit true asymptomatic individuals. Thus, we conducted a longitudinal cohort study to evaluate humoral- and cell-mediated responses to infection and vaccination in well-defined asymptomatic young adults (the Asymptomatic COVID-19 in Education [ACE] cohort).

METHODS

Asymptomatic testing services located at three UK universities identified asymptomatic young adults who were subsequently recruited with age- and sex-matched symptomatic and uninfected controls. Blood and saliva samples were collected after SARS-CoV-2 Wuhan infection, and again after vaccination. 51 participant's anti-spike antibody titres, neutralizing antibodies, and spike-specific T-cell responses were measured, against both Wuhan and Omicron B.1.1.529.1.

RESULTS

Asymptomatic participants exhibited reduced Wuhan-specific neutralization antibodies pre- and post-vaccination, as well as fewer Omicron-specific neutralization antibodies post-vaccination, compared to symptomatic participants. Lower Wuhan and Omicron-specific IgG titres in asymptomatic individuals were also observed pre- and post-vaccination, compared to symptomatic participants. There were no differences in salivary IgA levels. Conventional flow cytometry analysis and multi-dimensional clustering analysis indicated unvaccinated asymptomatic participants had significantly fewer Wuhan-specific IL-2 secreting CD4+ CD45RA+ T cells and activated CD8+ T cells than symptomatic participants, though these differences dissipated after vaccination.

CONCLUSIONS

Asymptomatic infection results in decreased antibody and T cell responses to further exposure to SARS-CoV-2 variants, compared to symptomatic infection. Post-vaccination, antibody responses are still inferior, but T cell immunity increases to match symptomatic subjects, emphasising the importance of vaccination to help protect asymptomatic individuals against future variants.

Uptake, effectiveness and safety of COVID-19 vaccines in individuals at clinical risk due to immunosuppressive drug therapy or transplantation procedures: a population-based cohort study in England

BACKGROUND

Immunocompromised individuals are at increased risk of severe COVID-19 outcomes, underscoring the importance of COVID-19 vaccination in this population. The lack of comprehensive real-world data on vaccine uptake, effectiveness and safety in these individuals presents a critical knowledge gap, highlighting the urgency to better understand and address the unique challenges faced by immunocompromised individuals in the context of COVID-19 vaccination.

METHODS

We analysed data from 12,274,946 people in the UK aged > 12 years from 01/12/2020 to 11/04/2022. Of these, 583,541 (4.8%) were immunocompromised due to immunosuppressive drugs, organ transplants, dialysis or chemotherapy. We undertook a cohort analysis to determine COVID-19 vaccine uptake, nested case-control analyses adjusted for comorbidities and sociodemographic characteristics to determine effectiveness of vaccination against COVID-19 hospitalisation, ICU admission and death, and a self-controlled case series assessing vaccine safety for pre-specified adverse events of interest.

RESULTS

Overall, 93.7% of immunocompromised individuals received at least one COVID-19 vaccine dose, with 80.4% having received three or more doses. Uptake reduced with increasing deprivation (hazard ratio [HR] 0.78 [95%CI 0.77-0.79] in the most deprived quintile compared to the least deprived quintile for the first dose). Estimated vaccine effectiveness against COVID-19 hospitalisation 2-6 weeks after the second and third doses compared to unvaccinated was 78% (95%CI 72-83) and 91% (95%CI 88-93) in the immunocompromised population, versus 85% (95%CI 83-86) and 86% (95%CI 85-89), respectively, for the general population. Results showed COVID-19 vaccines were protective against intensive care unit (ICU) admission and death in both populations, with effectiveness of over 92% against COVID-19-related death and up to 95% in reducing ICU admissions for both populations following the third dose. COVID-19 vaccines were generally safe for immunocompromised individuals, though specific doses of ChAdOx1, mRNA-1273 and BNT162b2 raised risks of specific cardiovascular/neurological conditions.

CONCLUSIONS

COVID-19 vaccine uptake is high in immunocompromised individuals on immunosuppressive drug therapy or who have undergone transplantation procedures, with documented disparities by deprivation. Findings suggest that COVID-19 vaccines are protective against severe COVID-19 outcomes in this vulnerable population, and show a similar safety profile in immunocompromised individuals and the general population, despite some increased risk of adverse events. These results underscore the importance of ongoing vaccination prioritisation for this clinically at-risk population to maximise protection against severe COVID-19 outcomes.

Invasive cervical cancer incidence following bivalent human papillomavirus vaccination: a population-based observational study of age at immunization, dose, and deprivation

BACKGROUND

High-risk human papillomavirus causes cervical cancer. Vaccines have been developed that significantly reduce the incidence of preinvasive and invasive disease. This population-based observational study used linked screening, immunization, and cancer registry data from Scotland to assess the influence of age, number of doses, and deprivation on the incidence of invasive disease following administration of the bivalent vaccine.

METHODS

Data for women born between January 1, 1988, and June 5, 1996, were extracted from the Scottish cervical cancer screening system in July 2020 and linked to cancer registry, immunization, and deprivation data. Incidence of invasive cervical cancer per 100 000 person-years and vaccine effectiveness were correlated with vaccination status, age at vaccination, and deprivation; Kaplan Meier curves were calculated.

RESULTS

No cases of invasive cancer were recorded in women immunized at 12 or 13 years of age irrespective of the number of doses. Women vaccinated at 14 to 22 years of age and given 3 doses of the bivalent vaccine showed a significant reduction in incidence compared with all unvaccinated women (3.2/100 000 [95% confidence interval (CI) = 2.1 to 4.6] vs 8.4 [95% CI = 7.2 to 9.6]). Unadjusted incidence was significantly higher in women from most deprived (Scottish Index of Multiple Deprivation 1) than least deprived (Scottish Index of Multiple Deprivation 5) areas (10.1/100 000 [95% CI = 7.8 to 12.8] vs 3.9 [95% CI = 2.6 to 5.7]). Women from the most deprived areas showed a significant reduction in incidence following 3 doses of vaccine (13.1/100 000 [95% CI = 9.95 to 16.9] vs 2.29 [95% CI = 0.62 to 5.86]).

CONCLUSION

Our findings confirm that the bivalent vaccine prevents the development of invasive cervical cancer and that even 1 or 2 doses 1 month apart confer benefit if given at 12-13 years of age. At older ages, 3 doses are required for statistically significant vaccine effectiveness. Women from more deprived areas benefit more from vaccination than those from less deprived areas.

Reaching the unreached through building trust: a mixed-method study on COVID-19 vaccination in rural Lao PDR

INTRODUCTION

The global COVID-19 vaccine rollout has been impacted by socioeconomic disparities and vaccine hesitancy, but few studies examine reasons for changed attitudes. In Lao People's Democratic Republic (Lao PDR), a nationwide government-led initiative was developed in response to COVID-19, focused on community health ownership and trust in primary healthcare. The intervention team including health and governance sectors conducted capacity-building workshops with local staff and community representatives and visited villages for vaccination outreach. This study investigates the impact of this intervention on COVID-19 vaccine acceptance in rural communities.

METHODS

Conducted in Xiengkhuang province, Lao PDR, from December 2022 to February 2023, the study employed a sequential mixed-methods research design. Data on vaccinated individuals from 25 villages were collected from 11 primary healthcare units; pre-post analysis was applied. Qualitative data, gathered through interviews and focus group discussions with villagers, village authorities, health staff and local government (n=102) in six villages, underwent inductive thematic analysis.

RESULTS

First-dose vaccine uptake after the intervention increased significantly (6.9 times). Qualitative analysis identified key reasons for vaccination hesitancy: (1) mistrust due to rumours and past experiences; (2) poor communication and inconsistent messaging and (3) challenges in access for priority groups. Influencing factors during the intervention included (1) effective local-context communication; (2) leveraging existing community structures and influential individuals in a multisectoral approach and (3) increased community motivation through improved satisfaction, ownership and relationships.

CONCLUSION

This study highlights the impact and methods of building trust with unreached populations in health interventions, emphasising locally led solutions. Successful reversal of vaccine hesitancy was achieved by addressing root causes and fostering ownership at community and local government levels through a 'positive approach'. This diverges from conventional supplemental immunisation activities and holds potential for systematically building trust between unreached populations and health systems. Further research could explore the impacts of routine vaccination for sustained improvements in health equity.