Long-term immunogenicity and immune persistence of live attenuated and inactivated hepatitis a vaccines: a report on additional observations from a phase IV study

Do vaccines increase or decrease susceptibility to diseases other than those they protect against?

Contrary to the long-held belief that the effects of vaccines are specific for the disease they were created; compelling evidence has demonstrated that vaccines can exert positive or deleterious non-specific effects (NSEs). In this review, we compiled research reports from the last 40 years, which were found based on the PubMed search for the epidemiological and immunological studies on the non-specific effects (NSEs) of the most common human vaccines. Analysis of information showed that live vaccines induce positive NSEs, whereas non-live vaccines induce several negative NSEs, including increased female mortality associated with enhanced susceptibility to other infectious diseases, especially in developing countries. These negative NSEs are determined by the vaccination sequence, the antigen concentration in vaccines, the type of vaccine used (live vs. non-live), and also by repeated vaccination. We do not recommend stopping using non-live vaccines, as they have demonstrated to protect against their target disease, so the suggestion is that their detrimental NSEs can be minimized simply by changing the current vaccination sequence. High IgG4 antibody levels generated in response to repeated inoculation with mRNA COVID-19 vaccines could be associated with a higher mortality rate from unrelated diseases and infections by suppressing the immune system. Since most COVID-19 vaccinated countries are reporting high percentages of excess mortality not directly attributable to deaths from such disease, the NSEs of mRNA vaccines on overall mortality should be studied in depth.

The infectivity and pathogenicity of Hepatitis A virus live-attenuated vaccine strain H2 in type I interferon receptor-deficient mice

Hepatitis A virus (HAV) live-attenuated vaccine H2 strain has been approved for clinical use for decades with ideal safety profiles in nonhuman primate models and humans. Recently, type I interferon (IFN) receptor-deficient mice were shown to be susceptible to HAV infection. Herein, we sought to determine the infection and replication dynamics of the H2 in Ifnar^−/− mice that lack type I IFN receptor. Following intravenous injection, the H2 failed to cause obvious clinical symptoms in Ifnar^−/− mice, and no significant upregulation in serum alanine aminotransferase (ALT) levels was observed. Notably, the histopathological examination showed that there were significant focal infiltrations of lymphocytes and neutrophils in the portal area, but no focal necrosis was observed in liver tissues. Viral RNAs sustained in the liver, and the infectious virus could be recovered from the liver tissue until 42 days post-infection. More importantly, H2 infection induced obvious viremia and persistent viral shedding in feces. In addition, robust HAV-specific humoral immune responses were induced in Ifnar^−/− mice. Overall, our study revealed the safety profile of H2 in Ifnar^−/− mice, which not only helps understand the attenuation mechanism of H2, but also expands the application of the Ifnar^−/− mouse model for HAV studies.

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We described the characteristics of Ifnar−/− mice infected by HAV H2 strain infection.

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H2 fails to induce ALT elevationand obvious liver damage in Ifnar−/− mice.

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H2 causes viremia, persistent viral shedding in feces, and replication in mice liver.

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H2 induces robust HAV-specific humoral immune responses in Ifnar^−/− mice.

The impact of different IPV-OPV sequential immunization programs on hepatitis A and hepatitis B vaccine efficacy

In recent years, the Global Polio Eradication Initiative has gradually implemented a global shift in polio immunization programs. Few studies cover polio immunization program impacts on the efficacy of other vaccines. This study investigated whether polio immunization programs affected hepatitis A (HepA) and hepatitis B (HepB) vaccination efficacy. Serum samples were collected from 968 infants before the first dose of polio vaccine, 28 days after completing primary polio immunization, and at 24 months old. Infants were classified into six polio immunization program groups: 1sIPV+2bOPV, 2sIPV+1bOPV, 2sIPV+1tOPV, 1cIPV+2bOPV, 2cIPV+1bOPV, and 2cIPV+1tOPV (sIPV: Sabin inactivated poliovirus vaccine; cIPV: Salk inactivated poliovirus vaccine; b, bivalent; t, trivalent; OPV, oral polio vaccine). No significant differences existed in antibody titers against HepA virus (anti-HAV) among the polio immunization program groups at any of the three time points (pre-first dose [p = 0.412], 28 days after primary immunization [p = 0.676], 24 months old [p = 0.556]). Before the first dose (p = 0.178) and at age 24 months (p = 0.987), no significant differences existed in HepB surface antibody (HBsAb) titers between the six polio immunization program groups). Twenty-eight days after primary immunization, no significant difference existed in HBsAb titers between groups after Bonferroni correction. Following HepA and HepB immunization, anti-HAV and HBsAb positivity reached > 98% in all groups, reflecting effective immunization. Our data suggest that different polio immunization programs did not affect HepA and HepB vaccine efficacy; HepA and HepB vaccines maintained high effectiveness irrespective of polio immunization program. This trial was registered on Clinical Trials.gov: NCT03614702.

Advances in the design and development of SARS-CoV-2 vaccines

Since the end of 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide. The RNA genome of SARS-CoV-2, which is highly infectious and prone to rapid mutation, encodes both structural and nonstructural proteins. Vaccination is currently the only effective method to prevent COVID-19, and structural proteins are critical targets for vaccine development. Currently, many vaccines are in clinical trials or are already on the market. This review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19, including viral vector vaccines, DNA vaccines, RNA vaccines, live-attenuated vaccines, inactivated virus vaccines, recombinant protein vaccines and bionic nanoparticle vaccines. In addition to traditional inactivated virus vaccines, some novel vaccines based on viral vectors, nanoscience and synthetic biology also play important roles in combating COVID-19. However, many challenges persist in ongoing clinical trials.

The Safety, Immunogenicity, and Immunopersistence of Hepatitis A Vaccine in HBs-Ag-Positive Participants: A Retrospective Study

Objectives

To compare the safety, immunogenicity, and immune persistence of hepatitis A (HA) vaccines between HBs-Ag-positive and -negative participants.

Method

9000 participants were enrolled in the phase IV study of live attenuated HA (HA-L) or inactivated HA (HA-I) vaccines. The HBs-Ag-positive subjects were detected and became an independent observation group. Adverse reactions (ARs), geometric mean concentrations (GMCs) and seroconversion rates (SRs) of the vaccines were analyzed at five time points until three years after vaccination. Results: 120 HBs-Ag-positive subjects were screened out, only 1 participant had grade 1 experienced ARs after HA-L injection. Except the time point of two years, the SRs of HBs-Ag-positive group were 100% for both vaccines. The GMCs were not statistically different between HBs-Ag-positive and -negative groups after the HA-L vaccination. The logarithmically transformed GMCs for HBs-Ag-positive and -negative groups were 3.21 mIU/mL (95% CI, 2.03-4.39 mIU/mL) and 2.95 mIU/mL (95% CI, 2.88-3.02 mIU/mL) 28 days after the HA-L vaccination, respectively.

Conclusions

Both HA-L and HA-I vaccines were safe for HBs-Ag-positive participants and may provide an excellent long-term protection against HAV in this study. The results indicated that people positive or negative for HBs-Ag can receive both HA-L and HA-I vaccines (ClinicalTrials.gov number, NCT02601040).

The excretion rate and stability of HAAg in human fecal samples after live attenuated hepatitis A vaccination

The live attenuated hepatitis A virus vaccine (HA-L) is in routine use in the Chinese national immunization program (NIP). The major disadvantages of HA-L include that theoretically, it may be possible for mutation shifts and secondary infections of the live vaccine viral strain. The aim of this study was to explore variation in the viral strain after vaccination with the HA-L. A total of 1297 fecal samples (including 470 for the 18 to 36-month-old age group, 527 for the 3 to 16-year-old group, and 300 for the 16 years and older group) were collected in the study, and the rate of hepatitis A virus (HAV) positivity in fecal samples was 11.36% (31/273), 11.44% (31/271), 9.70% (26/268), 8.47% (21/248), and 9.70% (23/237) on days 0, 7, 14, 21 and 28, respectively. A total of 77 HAV positive samples were randomly selected for VP1/2A (360 bp, 2218-2577) gene analysis. Phylogenetic trees were then constructed by the neighbor-joining method. Phylogenetic analyses showed that all the isolated HAV strains belonged to sub-genotype IB, which was the same as the vaccine strain. Compared with the vaccine strain, HM-175/7MK-5 (M16632.1), there were only two base mutations discovered, at 2291 and 2568. However, the amino acid mutation analysis showed that those base mutations were synonymous mutations. The isolated HAV strains were genetically stable. This study provides a reference for the safety concern regarding the routine and wide-range use in people older than 18 months.

The impact of universal live attenuated hepatitis A vaccines in Henan, China, 2005-2018

OBJECTIVES

To analyze the effects of one dose of live attenuated hepatitis A vaccine in a developing country.

METHODS

The reported cases of hepatitis A virus (HAV) infection from 2005 to 2018 in Henan province, China, were analyzed. Data of vaccinated children were assessed on the childhood immunization information management system. Questionnaire survey and blood sample collection were randomly conducted in six counties and districts of Henan province to analyze the prevalence of HAV lgG among the population aged 0-70 years.

RESULTS

In 2008, Henan province began to expand its program on immunization, and children aged 18 months were given one dose of live attenuated hepatitis A vaccine (HepA-L). From 2005 to 2007, the HAV incidence remained steady at above 5000 cases per year and increased to 7489 in 2007. Since 2008, the HAV incidence decreased cumulatively from 4576 to 237 in 2018, indicating a 94.8% decrease, which was particularly pronounced among adolescents (98.2%). The proportion of hepatitis A cases in patients younger than 10 years continually decreased from 41.6% in 2012 to 3.8% in 2018. The reduction of reported cases older than 40 years was slower than that of children. In 2012, the proportion of hepatitis A cases older than 40 years was 27.6%, and continually increased to 69.2% (164/237) in 2018. The results of serological investigation showed that the 0-1.5-year age group had the lowest anti-HAV IgG prevalence (38.6%), which increased to 75.0% in the 4-6-year age group, covered by this immunization program.

CONCLUSIONS

The data indicated a large decrease in HAV infections in Henan province from 2008 onward in response to the introduction of a planned immunization program of HepA-L.