Live-virus vaccines in pregnancy. Risks and recommendations

Mpox virus mRNA-lipid nanoparticle vaccine candidates evoke antibody responses and drive protection against the Vaccinia virus challenge in mice

In response to the human Mpox (hMPX) epidemic that began in 2022, there is an urgent need for a monkeypox vaccine. Here, we have developed a series of mRNA-lipid nanoparticle (mRNA-LNP)-based vaccine candidates that encode a collection of four highly conserved Mpox virus (MPXV) surface proteins involved in virus attachment, entry, and transmission, namely A29L, A35R, B6R, and M1R, which are homologs to Vaccinia virus (VACV) A27, A33, B5, and L1, respectively. Despite possible differences in immunogenicity among the four antigenic mRNA-LNPs, administering these antigenic mRNA-LNPs individually (5 μg each) or an average mixture of these mRNA-LNPs at a low dose (0.5 μg each) twice elicited MPXV-specific IgG antibodies and potent VACV-specific neutralizing antibodies. Furthermore, two doses of 5 μg of A27, B5, and L1 mRNA-LNPs or a 2 μg average mixture of the four antigenic mRNA-LNPs protected mice against weight loss and death after the VACV challenge. Overall, our data suggest that these antigenic mRNA-LNP vaccine candidates are both safe and efficacious against MPXV, as well as diseases caused by other orthopoxviruses.

Monkeypox and the perinatal period: what does maternal-fetal medicine need to know?

BACKGROUND

After the global elimination of smallpox, monkeypox has become the most threatening orthopoxvirus to human health. Very few studies have been reported on pregnant women and newborns. In the case of monkeypox infection, the virus can cause serious adverse pregnancy events in women, which can lead to fetal or neonatal death.

DATA SOURCES

We made a comprehensive review after an extensive literature search in the PubMed/Medline database and websites concerning smallpox and monkeypox.

RESULTS

Two case reports reported a total of nine pregnant women, six of whom had fetal deaths. In the autopsy of a stillbirth, researchers found that the placenta was infected with monkeypox virus, but the mechanism of infection remains unclear. Smallpox vaccine should be administered to acutely exposed pregnant women and newborns. Several novel recombinant vaccinia immunogloblin (rVIG) and human-specific monoclonal antibodies are being developed for the prevention and treatment of monkeypox virus infection. After the fetus was delivered, the newborn should take a bath as soon as possible to remove the amniotic fluid and dirt from the body. The appropriate isolation protocol for the newborn should be selected according to the infection status of the mother. It is not known whether monkeypox virus is present in breast milk, and pasteurized breast milk can be given to newborns when breastfeeding is considered.

CONCLUSION

This review presents an overview of monkeypox in the perinatal period and guides the future research direction.

Monkeypox in pregnancy: virology, clinical presentation, and obstetric management

The 2022 monkeypox outbreak, caused by the zoonotic monkeypox virus, has spread across 6 World Health Organization regions (the Americas, Africa, Europe, Eastern Mediterranean, Western Pacific, and South-East Asia) and was declared a public health emergency of international concern on July 23, 2022. The global situation is especially concerning given the atypically high rate of person-to-person transmission, which suggests viral evolution to an established human pathogen. Pregnant women are at heightened risk of vertical transmission of the monkeypox virus because of immune vulnerability and natural depletion of population immunity to smallpox among reproductive-age women, and because orthopoxviral cell entry mechanisms can overcome the typically viral-resistant syncytiotrophoblast barrier within the placenta. Data on pregnancy outcomes following monkeypox infection are scarce but include reports of miscarriage, intrauterine demise, preterm birth, and congenital infection. This article forecasts the issues that maternity units might face and proposes guidelines to protect the health of pregnant women and fetuses exposed to the monkeypox virus. We review the pathophysiology and clinical features of monkeypox infection and discuss the obstetrical implications of the unusually high prevalence of anogenital lesions. We describe the use of real-time polymerase chain reaction tests from mucocutaneous and oropharyngeal sites to confirm infection, and share an algorithm for the antenatal management of pregnant women with monkeypox virus exposure. On the basis of the best available knowledge from prenatal orthopoxvirus infections, we discuss the sonographic features of congenital monkeypox and the role of invasive testing in establishing fetal infection. We suggest a protocol for cesarean delivery to avoid the horizontal transmission of the monkeypox virus at birth and address the controversy of mother-infant separation in the postpartum period. Obstetrical concerns related to antiviral therapy with tecovirimat and vaccinia immune globulin are highlighted, including the risks of heart rate-corrected QT-interval prolongation, inaccuracies in blood glucose monitoring, and the predisposition to iatrogenic venous thromboembolism. The possibility of monkeypox vaccine hesitancy during pregnancy is discussed, and strategies are offered to mitigate these risks. Finally, we conclude with a research proposal to address knowledge gaps related to the impact of monkeypox infection on maternal, fetal, and neonatal health.

Prospective safety surveillance study of ACAM2000 smallpox vaccine in deploying military personnel

OBJECTIVES

To compare rates of myopericarditis, severe and serious dermatological or neurological events, and other adverse events in deploying US military personnel who received or did not receive ACAM2000® (Smallpox [Vaccinia] Vaccine, Live) vaccine and to evaluate potential risk factors for development of myopericarditis.

METHODS

Prospective observational cohort study enrolling up to 15,000 ACAM2000 recipients (Cohort 1) and up to 5000 persons otherwise eligible for ACAM2000 vaccination but not vaccinated due to recency of vaccination or characteristics of their contacts (Cohort 2). Data and specimens were collected initially and 10 (6-17) days later. Those with clinical or laboratory evidence of possible myopericarditis were referred for further evaluation and adjudication by a blinded independent review committee. The adjusted odds ratio for myopericarditis was determined by a logistic regression model controlling for age, race, gender, and exercise regimen.

RESULTS

14,667 subjects provided initial data and specimens (Cohort 1, 10,825; Cohort 2, 3842); 12,110 (Cohort 1, 8945; Cohort 2, 3165) completed Visit 2 per-protocol. A total of 125 (Cohort 1, 111; Cohort 2, 14) were referred for myopericarditis adjudication, yielding 54 (Cohort 1, 44, Cohort 2, 10) subclinical myopericarditis, 5 suspected myocarditis, 1 confirmed myocarditis, and 1 suspected pericarditis. Unadjusted myopericarditis rates were: Cohort 1, 5.7/1000 (95% CI, 4.3-7.5); Cohort 2, 3.2/1000 (95% CI, 1.7-5.8). Unadjusted and adjusted odds ratios for myopericarditis were 1.8 (95% CI: 0.9-3.6) and 1.3 (95% CI: 0.6-2.6), respectively. One hundred seventeen subjects (1.1%) in Cohort 1 and 13 (0.3%) in Cohort 2 experienced at least 1 serious adverse event. No instances of serious and severe neurological or dermatological adverse events were reported.

CONCLUSIONS

In this carefully screened, generally young and healthy service-member population, ACAM2000 vaccination was associated with modest non-significant increases in the risk of myopericarditis (adjusted OR, 1.3; unadjusted OR, 1.8); all but seven cases were subclinical.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov NCT00928577.

Protective Efficacy of a Chimeric Insect-Specific Flavivirus Vaccine against West Nile Virus

Virulent strains of West Nile virus (WNV) are highly neuro-invasive and human infection is potentially lethal. However, no vaccine is currently available for human use. Here, we report the immunogenicity and protective efficacy of a vaccine derived from a chimeric virus, which was constructed using the structural proteins (prM and E) of the Kunjin strain of WNV (WNV_KUN) and the genome backbone of the insect-specific flavivirus Binjari virus (BinJV). This chimeric virus (BinJ/WNV_KUN-prME) exhibits an insect-specific phenotype and does not replicate in vertebrate cells. Importantly, it authentically presents the prM-E proteins of WNV_KUN, which is antigenically very similar to other WNV strains and lineages. Therefore BinJ/WNV_KUN-prME represents an excellent candidate to assess as a vaccine against virulent WNV strains, including the highly pathogenic WNV_NY99. When CD1 mice were immunized with purified BinJ/WNV_KUN-prME, they developed robust neutralizing antibody responses after a single unadjuvanted dose of 1 to 5 μg. We further demonstrated complete protection against viremia and mortality after lethal challenge with WNV_NY99, with no clinical or subclinical pathology observed in vaccinated animals. These data suggest that BinJ/WNV_KUN-prME represents a safe and effective WNV vaccine candidate that warrants further investigation for use in humans or in veterinary applications.

Analysis of pregnancy and infant health outcomes among women in the National Smallpox Vaccine in Pregnancy Registry who received Anthrax Vaccine Adsorbed

The National Smallpox Vaccine in Pregnancy Registry (NSVIPR) actively follows women inadvertently vaccinated with smallpox vaccine during or shortly before pregnancy to evaluate their reproductive health outcomes. Approximately 65% of NSVIPR participants also inadvertently received Anthrax Vaccine Adsorbed (AVA) while pregnant, providing a ready opportunity to evaluate pregnancy and infant health outcomes among these women. AVA-exposed pregnancies were ascertained using NSVIPR and electronic healthcare data. Rates of pregnancy loss and infant health outcomes, including major birth defects, were compared between AVA-exposed and AVA-unexposed pregnancies. Analyses included AVA-exposed and AVA-unexposed pregnant women who also received smallpox vaccine 28 days prior to or during pregnancy. Rates of adverse outcomes among the AVA-exposed group were similar to or lower than expected when compared with published reference rates and the AVA-unexposed population. The findings provide reassurance of the safety of AVA when inadvertently received by a relatively young and healthy population during pregnancy.

Human antibody responses to the polyclonal Dryvax vaccine for smallpox prevention can be distinguished from responses to the monoclonal replacement vaccine ACAM2000

Dryvax (Wyeth Laboratories, Inc., Marietta, PA) is representative of the vaccinia virus preparations that were previously used for preventing smallpox. While Dryvax was highly effective, the national supply stocks were depleted, and there were manufacturing concerns regarding sterility and the clonal heterogeneity of the vaccine. ACAM2000 (Acambis, Inc./Sanofi-Pasteur Biologics Co., Cambridge, MA), a single-plaque-purified vaccinia virus derivative of Dryvax, recently replaced the polyclonal smallpox vaccine for use in the United States. A substantial amount of sequence heterogeneity exists within the polyclonal proteome of Dryvax, including proteins that are missing from ACAM2000. Reasoning that a detailed comparison of antibody responses to the polyclonal and monoclonal vaccines may be useful for identifying unique properties of each antibody response, we utilized a protein microarray comprised of approximately 94% of the vaccinia poxvirus proteome (245 proteins) to measure protein-specific antibody responses of 71 individuals receiving a single vaccination with ACAM2000 or Dryvax. We observed robust antibody responses to 21 poxvirus proteins in vaccinated individuals, including 11 proteins that distinguished Dryvax responses from ACAM2000. Analysis of protein sequences from Dryvax clones revealed amino acid level differences in these 11 antigenic proteins and suggested that sequence variation and clonal heterogeneity may contribute to the observed differences between Dryvax and ACAM2000 antibody responses.

Animal poxvirus vaccines: a comprehensive review

The family Poxviridae includes several viruses of medical and veterinary importance. Global concerted efforts combined with an intensive mass-vaccination campaign with highly efficaceious live vaccine of vaccinia virus have led to eradication of smallpox. However, orthopoxviruses affecting domestic animals continue to cause outbreaks in several endemic countries. Different kinds of vaccines starting from conventional inactivated/attenuated to recombinant protein-based vaccines have been used for control of poxvirus infections. Live virus homologous vaccines are currently in use for diseases including capripox, parapox, camelpox and fowlpox, and these vaccines are highly effective in eliciting (with the exception of parapoxviruses) long-lasting immunity. Attenuated strains of poxviruses have been exploited as vectored vaccines to deliver heterologous immunogens, many of them being licensed for use in animals. Worthy of note are vaccinia virus, fowlpox virus, capripoxvirus, parapoxvirus and canary pox, which have been successfully used for developing new-generation vaccines targeting many important pathogens. Remarkable features of these vaccines are thermostability and their ability to engender both cellular and humoral immune responses to the target pathogens. This article updates the important vaccines available for poxviruses of livestock and identifies some of the research gaps in the present context of poxvirus research.

Background rates of adverse pregnancy outcomes for assessing the safety of maternal vaccine trials in sub-Saharan Africa

Background

Maternal immunization has gained traction as a strategy to diminish maternal and young infant mortality attributable to infectious diseases. Background rates of adverse pregnancy outcomes are crucial to interpret results of clinical trials in Sub-Saharan Africa.

Methods

We developed a mathematical model that calculates a clinical trial's expected number of neonatal and maternal deaths at an interim safety assessment based on the person-time observed during different risk windows. This model was compared to crude multiplication of the maternal mortality ratio and neonatal mortality rate by the number of live births. Systematic reviews of severe acute maternal morbidity (SAMM), low birth weight (LBW), prematurity, and major congenital malformations (MCM) in Sub-Saharan African countries were also performed.

Findings

Accounting for the person-time observed during different risk periods yields lower, more conservative estimates of expected maternal and neonatal deaths, particularly at an interim safety evaluation soon after a large number of deliveries. Median incidence of SAMM in 16 reports was 40.7 (IQR: 10.6–73.3) per 1,000 total births, and the most common causes were hemorrhage (34%), dystocia (22%), and severe hypertensive disorders of pregnancy (22%). Proportions of liveborn infants who were LBW (median 13.3%, IQR: 9.9–16.4) or premature (median 15.4%, IQR: 10.6–19.1) were similar across geographic region, study design, and institutional setting. The median incidence of MCM per 1,000 live births was 14.4 (IQR: 5.5–17.6), with the musculoskeletal system comprising 30%.

Interpretation

Some clinical trials assessing whether maternal immunization can improve pregnancy and young infant outcomes in the developing world have made ethics-based decisions not to use a pure placebo control. Consequently, reliable background rates of adverse pregnancy outcomes are necessary to distinguish between vaccine benefits and safety concerns. Local studies that quantify population-based background rates of adverse pregnancy outcomes will improve safety assessment of interventions during pregnancy.

Pregnancy discovered after smallpox vaccination: Is vaccinia immune globulin appropriate?

Smallpox vaccination just before conception or during pregnancy can result, in rare instances, in fetal vaccinia from viral infection of the fetus. Approximately 50 cases have been documented, despite literally billions of people having been vaccinated. This live viral vaccine has a wider array of rare but serious medical side effects (eg, eczema vaccinatum, progressive vaccinia, encephalitis, myopericarditis) compared with other vaccines that are given currently to the public. In response to recent world events, the Centers for Disease Control and Prevention and the United States Department of Defense established a preoutbreak smallpox vaccination program. Because no actual outbreak has yet occurred, some investigators have proposed prophylactic treatment with vaccinia immune globulin for pregnancies that are exposed to smallpox vaccine to prevent fetal vaccinia. We review the existing medical literature to access the risks of fetal vaccinia in these pregnancies and the controversy regarding the prophylactic use of vaccinia immune globulin.

Smallpox: vaccine reactions and contraindications

Concern regarding the use of smallpox for bioterrorism has led to the reintroduction of smallpox vaccination. The historic background leading to protective methods against smallpox disease, the adverse reactions and contraindications associated with vaccination, and the ongoing development of potentially safer smallpox vaccines are reviewed here.

The role of the obstetrician-gynecologist in emerging infectious diseases: monkeypox and pregnancy

Early in June 2003, the Centers for Disease Control and Prevention (CDC) announced yet another unique infectious disease outbreak, the first evidence of community-acquired monkeypox in the United States. By July 8, 2003, a total of 71 cases had been reported to CDC from 6 states. When emerging infectious diseases are reported in the United States, particularly when these reports receive widespread media attention, obstetrician-gynecologists may be called upon to rapidly respond to queries from their patients and to address certain infectious disease risks within their clinical practices. In addition, obstetrician-gynecologists may have specific concerns about the implications for an infectious disease outbreak, such as monkeypox, for pregnant women. Therefore, it is important that obstetrician-gynecologists know how to gather up-to-date and accurate information about infectious disease outbreaks and that they be familiar with the public health response system for responding to such outbreaks.

Vaccinia virus infection during murine pregnancy: a new pathogenesis model for vaccinia fetalis

Vaccinia fetalis, the vertical transfer of vaccinia virus from mother to fetus, is a relatively rare but often fatal complication of primary vaccinia virus vaccination during pregnancy. To date there has been no attempt to develop an animal model to study the pathogenesis of this acute viral infection in vivo. Here we report that infection of gestating BALB/c mice by either intravenous or intraperitoneal routes with the Western Reserve strain of vaccinia virus results in the rapid colonization of the placenta and vertical transfer of virus to the developing fetus. Systemic maternal infections during gestation lead to the death of all offspring prior to or very shortly after birth. Using in situ hybridization for vaccinia virus mRNA to identify infected cells, we show that the virus initially colonizes cells lining maternal lacunae within the trophospongium layer of the placenta. The study of this model will significantly enhance our understanding of the pathogenesis of fetal vaccinia virus infections and aid in the development of effective treatments designed to reduce the risk of vaccinia virus-associated complications during pregnancy.

Smallpox infections during pregnancy, lessons on pathogenesis from nonpregnant animal models of infection

Both vaccinated and unvaccinated women during pregnancy who contract variola virus, the causative agent of smallpox, suffer much higher mortality rates than nonpregnants. Furthermore, acute maternal smallpox leads to spontaneous abortion, premature termination of pregnancy and early postnatal infant mortality. The mechanisms governing the abortifacient activity of smallpox, as well as the enhanced susceptibility of gestating women to lethal disease, have remained largely unexamined. Experimental poxvirus infections in nonpregnant small animal models have revealed that T helper type 1 (TH1) cytokines promote efficient resolution of these infections whereas type 2 (TH2) cytokines enhance viral pathogenesis. These data, combined with recent understanding of how the immune system is modulated by pregnancy, may offer important clues as to the increased pathogenesis of variola in pregnant women. The aim of this review is to bring together the current literature on the effects of poxvirus infections in nonpregnant hosts, as well as the effects of pregnancy on the immune system, in order to develop unifying concepts that may provide insight into the pathogenesis of variola during pregnancy and why prior vaccination with vaccinia virus the live anti-variola vaccine offers less protection to pregnant women and their unborn children.

The new cell culture smallpox vaccine should be offered to the general population

A series of major factors must be weighed in deciding whether or not, and to what extent, a particular country should consider pre-exposure vaccination for smallpox. These include the risk of a bioterrorist attack using smallpox, the risk of secondary spread from another country, the risks and benefits of vaccination, the effectivenes s of vaccination pre- and post-exposure, the prevalence of immunocompromised persons, the capacity of the medical care delivery system and the wealth of a nation. We review here the issues and variables relevant for policy making, propose a framework for country-specific decision making and suggest the World Health Organization has a key role to play, particularly with regard to lower-income countries. In doing so, we support the proposition.

Medical management of vulnerable populations and co-morbid conditions of victims of bioterrorism

Planning for the medical response to bioterrorism has primarily focused around the needs of the population as a whole. There has been little discussion pertaining to certain vulnerable groups such as children, pregnant women, or immunocompromised patients, yet they will likely comprise a significant subset of the exposed population. In addition, they will be at increased risk for morbidity and mortality following an attack. The emergency response to bioterrorism will be more complex as it relates to these vulnerable populations. Careful consideration of their special needs, some of which are presented in this article, may refine our efforts.

In vitro infection of human placental trophoblast by wild-type vaccinia virus and recombinant virus expressing HIV envelope glycoprotein

Short-time (< or = 7 days) cultures of trophoblast mononuclear cells isolated from term placentae were challenged with vaccinia virus. Cytopathic effects were induced in crude placental cell preparations as well as in cultures established after negative immunosorting of major histocompatibility complex class I epitope-expressing cells, i.e. cultures exclusively derived from villous cytotrophoblast according to our present state of knowledge. The trophoblast in vitro supported a full replicative cycle of both wild-type viruses and a recombinant clone serving as a vector for the human immunodeficiency virus type 1 envelope gene. Results may shed light on mechanisms involved in the rarely observed foetal damage caused by smallpox vaccination during pregnancy.

Outbreak of poliomyelitis in Finland in 1984. Description of nine cases with persisting paralysis

Finland has been free of poliomyelitis since 1964 following a high coverage regular immunization programme using the Salk-type trivalent inactivated poliovirus vaccine. In late 1984 an outbreak of poliomyelitis with widespread circulation of poliovirus type 3 throughout the country was found. A thorough surveillance revealed 9 sporadic cases with acute persisting paralysis, all shown to be caused by poliovirus type 3. The preceding 20-year period free from poliomyelitis contributed to some diagnostic problems.

Vaccinial osteomyelitis in a case of generalized intrauterine virus infection

We report the case of a 14-week fetus who developed a generalized vaccinia virus infection after primary vaccination of the mother in the 10th week of pregnancy. Special emphasis is given to the skeletal lesions, which have not been previously reported in prenatal vaccinial infection.

The clinical management of repeated early pregnancy wastage

A rational systematic evaluation is essential to the management of a couple with repeated early pregnancy wastage. Psychologic support in the form of frequent discussions and sympathetic counseling are crucial to the successful evaluation and treatment of the anxious couple. A prompt and orderly evaluation will relieve anxiety. When no etiologic factor is identified, a 60% to 80% fetal salvage rate may be expected. Once a patient conceives, serial ultrasonography, beta-hCG determination, and estradiol determination may be useful in detecting the stage of the embryonic death if subsequent abortion occurs. A karyotypic analysis of the products of conception should be performed if fetal loss occurs.

Drugs in pregnancy and lactation

The hazards of exposing the human fetus to drugs have become increasingly apparent in the last 15 years, during which time drug usage has steadily increased. Even though a direct cause-and-effect relationship between certain commonly used drugs and fetal disorders or malformations has been difficult to establish, the principle of avoidance of all but essential medications in pregnancy and in the potentially pregnant has become increasingly important. This paper summarizes the factors determining fetal damage and lists the problems associated with some drugs frequently encountered in practice.