Why Should We Advocate Maternal Immunization?

Deferring Risk: Limitations to the Evidence in Product Labels for Vaccine Use in Pregnancy

Background: The gaps in clinical trial evidence about vaccination in pregnancy have serious implications for health care worker and public misunderstandings. Contradictions between National Immunization Technical Advisory Group (NITAG) recommendations and regulatory product labeling information contribute to misinformation about vaccine safety and effectiveness. Methods: A mixed methods approach that included a stakeholder consensus decision-making workshop and a national survey of Canadian health care providers (HCPs). Results: We identified knowledge gaps and serious limitations concerning the information in vaccine product labels. Stakeholders were troubled that some HCPs rely on regulatory product labels to inform their decisions without knowing their limitations in content. Our survey showed that HCPs were uncertain about the purpose of product labels and the evidence contained in them. Over a third of respondents incorrectly thought that product labels and NITAG recommendations are based on the same evidence and that the information they contain is regularly updated. Conclusions: Applying social risk theories, we show how such gaps in information defer responsibility for decisions about disease risk and vaccine safety from regulatory agencies and vaccine manufacturers onto HCPs and their clients. This may be especially relevant for COVID-19 and other emerging vaccines that are initially authorized for conditional or emergency use, and especially in understudied populations such as pregnant people. More frequent updating and alignment of robust, unbiased, and independently reviewed clinical trial and postmarket safety and effectiveness evidence with NITAG recommendations would allay HCP and public misunderstandings.

Transplacental Antibody Transfer of Respiratory Syncytial Virus Specific IgG in Non-Human Primate Mother-Infant Pairs

One approach to protect new-borns against respiratory syncytial virus (RSV) is to vaccinate pregnant women in the last trimester of pregnancy. The boosting of circulating antibodies which can be transferred to the foetus would offer immune protection against the virus and ultimately the disease. Since non-human primates (NHPs) have similar reproductive anatomy, physiology, and antibody architecture and kinetics to humans, we utilized this preclinical species to evaluate maternal immunization (MI) using an RSV F subunit vaccine. Three species of NHPs known for their ability to be infected with human RSV in experimental challenge studies were tested for RSV-specific antibodies. African green monkeys had the highest overall antibody levels of the old-world monkeys evaluated and they gave birth to offspring with anti-RSV titers that were proportional to their mother. These higher overall antibody levels are associated with greater durability found in their offspring. Immunization of RSV seropositive AGMs during late pregnancy boosts RSV titers, which consequentially results in significantly higher titers in the vaccinated new-borns compared to the new-borns of unvaccinated mothers. These findings, accomplished in small treatment group sizes, demonstrate a model that provides an efficient, resource sparing and translatable preclinical in vivo system for evaluating vaccine candidates for maternal immunization.

Coadministration of Anti-Viral Monoclonal Antibodies With Routine Pediatric Vaccines and Implications for Nirsevimab Use: A White Paper

Routine childhood vaccinations are key for the protection of children from a variety of serious and potentially fatal diseases. Current pediatric vaccine schedules mainly cover active vaccines. Active vaccination in infants is a highly effective approach against several infectious diseases; however, thus far, for some important viral pathogens, including respiratory syncytial virus (RSV), vaccine development and license by healthcare authorities have not been accomplished. Nirsevimab is a human-derived, highly potent monoclonal antibody (mAb) with an extended half-life for RSV prophylaxis in all infants. In this manuscript, we consider the potential implications for the introduction of an anti-viral mAb, such as nirsevimab, into the routine pediatric vaccine schedule, as well as considerations for coadministration. Specifically, we present evidence on the general mechanism of action of anti-viral mAbs and experience with palivizumab, the only approved mAb for the prevention of RSV infection in preterm infants, infants with chronic lung disease of prematurity and certain infants with hemodynamically significant heart disease. Palivizumab has been used for over two decades in infants who also receive routine vaccinations without any alerts concerning the safety and efficacy of coadministration. Immunization guidelines (Advisory Committee on Immunization Practices, Joint Committee on Vaccination and Immunization, National Advisory Committee on Immunization, Centers for Disease Control and Prevention, American Academy of Pediatrics, The Association of the Scientific Medical Societies in Germany) support coadministration of palivizumab with routine pediatric vaccines, noting that immunobiologics, such as palivizumab, do not interfere with the immune response to licensed live or inactivated active vaccines. Based on the mechanism of action of the new generation of anti-viral mAbs, such as nirsevimab, which is highly specific targeting viral antigenic sites, it is unlikely that it could interfere with the immune response to other vaccines. Taken together, we anticipate that nirsevimab could be concomitantly administered to infants with routine pediatric vaccines during the same clinic visit.

Healthcare providers' interpretations of product labelling information developed through a consensus stakeholder approach

BACKGROUND

The World Health Organization recommends immunization with inactivated influenza vaccine (IIV) and tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy. Yet, product labelling information for IIV and Tdap sends a different message. In a previous study, we developed evidence-based statements about vaccination in pregnancy that could be included in product information. This study compares healthcare providers' perceptions of the revised statements to those currently used in vaccine product labelling information.

METHODS

A 30-item online survey with qualitative and quantitative components was distributed to Canadian maternal healthcare providers via professional organizations and public health. Participants read excerpts from revised and existing IIV and Tdap product labelling information and answered questions about how they perceived the safety and effectiveness of the vaccines, whether they would recommend each vaccine during pregnancy, and which statements they preferred.

RESULTS

From June to August 2018, 449 healthcare providers completed the survey, including physicians (45%), nurses (24%), midwives (27%) and others (5%). Most participants perceived the vaccines to be safe and effective based on the revised statements. Over twice as many participants said they would recommend the IIV and Tdap vaccines in pregnancy based on the revised rather than the existing statements (64% versus 21% for IIV and 63% versus 27% for Tdap). Most participants selected that the revised statements better explained the risks and benefits of vaccination in pregnancy (65% versus 21% for IIV; 51% versus 27% for Tdap). Qualitative comments highlighted the strengths of the revised statements and areas for improvement.

CONCLUSIONS

The majority of participants demonstrated preferences for the revised IIV and Tdap product label statements over the existing statements. Comments suggested the revised statements include improvements to the evidence-base and readability. Involving stakeholders improved the development of product labelling information, but further improvement is needed to support the evidence-based use of vaccines in pregnancy.

Passive immunity in newborn from SARS-CoV-2-infected mother

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vertical transmission is an open issue. Recent reports call into question in utero or peripartum viral transmission to the offspring. Few data are available on immunoglobulin G (IgG) and/or IgM in newborns. Insufficient evidence is available regarding passive immunity in neonates born from SARS-CoV-2 infected women. We report a case of a neonate showing the presence of blood specific IgG and the absence of IgM and negative nasopharyngeal swab. He was born from an asymptomatic SARS-CoV-2-infected mother with positive IgG and IgM. The transplacental passage of specific IgG antibodies from the affected mother to the unaffected fetus highlights neonatal passive immunity.

The journey to a respiratory syncytial virus vaccine

OBJECTIVE

The high burden associated with respiratory syncytial virus (RSV) has made the development of RSV vaccine(s) a global health high priority. This review summarizes the journey to an RSV vaccine, the different strategies and challenges associated with the development of preventive strategies for RSV, and the diverse products that are undergoing clinical testing.

DATA SOURCES

Studies on RSV biology, immunology, epidemiology, and monoclonal antibodies (mAbs) and vaccines were searched using MEDLINE. We also searched PATH.org and ClinicalTrials.gov for updated information regarding the status of RSV vaccines and mAbs undergoing clinical trials.

STUDY SELECTIONS

We selected relevant studies conducted in infants and young children, pregnant women, and elderly population for the prevention of RSV infection.

RESULTS

Identification of a safe and immunogenic vaccine has been an important but elusive initiative for more than 60 years for different reasons, including the legacy of formalin-inactivated vaccine, our limited understanding of the immune response to RSV and how it relates to clinical disease severity, or the need for different end points according to the different vaccine platforms. Nevertheless, there are currently 39 vaccines and mAbs under development and 19 undergoing clinical trials.

CONCLUSION

Over the past decade, there have been significant advances in our knowledge of RSV molecular and structural biology and in understanding the human immune response to RSV. Despite the barriers, there are several promising mAbs and RSV vaccines undergoing clinical trials that hope to offer protection to the most vulnerable populations.