Logan Reed
The Zika virus (ZIKV) is a mosquito-borne flavivirus that was first isolated in Uganda in 1947 and has since spread to many countries worldwide. The virus can cause serious birth defects, and its association with congenital diseases such as microcephaly and Guillain-Barré syndrome has prompted global efforts to develop a vaccine. Currently, there is no vaccine or medicine available to prevent or treat Zika virus infections, but several candidates are undergoing clinical trials. These include nucleic acid vaccines, inactivated vaccines, viral-vectored vaccines, and attenuated vaccines, with some showing promising results in animal studies and early-stage human trials. The development of a Zika vaccine faces challenges due to the decreased prevalence of the virus, which makes it difficult to conduct phase III efficacy trials. However, organizations like UNICEF, WHO, and PAHO are working to expedite the process and address gaps in vaccine development and diagnostic tools.
| Characteristics | Values |
|---|---|
| Current vaccines available | None |
| Vaccines in development | DNA vaccines, mRNA vaccines, live attenuated vaccines, whole inactivated vaccines, peptide-based vaccines, protein-based vaccines, monoclonal antibodies (MAbs), vaccines targeting vector-derived antigens, purified inactivated vaccines, chimeric vaccines |
| Organisations involved in vaccine development | CDC, WHO, PAHO, UNICEF, private companies |
| Obstacles to vaccine development | Decreased prevalence of Zika virus, insufficient mosquito control, insufficient understanding of viral disease mechanism, insufficient understanding of immune evasion mechanisms, long and complex development process |
| Potential benefits of a vaccine | Reduction in Zika congenital syndrome, prevention of negative effects on unborn children, prevention of Zika-associated diseases in women of childbearing age |
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What You'll Learn
There is currently no vaccine to prevent Zika virus infections
Various vaccine platforms have been evaluated, including DNA, mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, peptide and protein-based vaccines, and passive immunizations using monoclonal antibodies (MAbs). In 2016, the Zika virus outbreak spread to the Americas, causing a spectrum of congenital diseases, including microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults. This unprecedented epidemic and its associated serious diseases prompted the global research community to rapidly develop safe and efficacious vaccines.
Several Zika virus vaccine candidates have shown significant promise in human clinical trials, including nucleic acid vaccines, inactivated vaccines, viral-vectored vaccines, and attenuated vaccines. The only vaccination with clinical data is the ZIPV vaccine, a whole inactivated vaccine from the Puerto Rican strain PRVABC59. Studies in mice and non-human primates have shown high levels of protection against viraemia following challenges with multiple Zika strains, with no adverse side effects and high levels of seroconversion (92%).
Despite these promising developments, there are currently no vaccines on the market against ZIKV. UNICEF, along with WHO and PAHO, is working to advance research and development to address gaps in vaccine and diagnostic tools. The Zika virus vaccine project aims to support and accelerate the development and scale-up of vaccines to prevent ZIKV infection and its negative effects on unborn children. While there is currently no vaccine to prevent Zika virus infections, ongoing research and collaborative efforts provide hope for a future vaccine to address this public health concern.
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The development of peptide-based vaccines is underway
There is currently no vaccine to prevent or medicine to treat the Zika virus. The Zika virus, first isolated in Uganda in 1947, is primarily spread by mosquitoes and can cause serious birth defects. In 2016, the World Health Organization (WHO) declared it a Public Health Emergency of International Concern.
Following the 2017 Zika virus outbreak, multiple public and private organizations began research initiatives to develop a safe and effective vaccine. The development of peptide-based vaccines is one approach that is currently underway. Peptide-based vaccines are composed of 20-30 amino acids made of synthetic B- or T-cells epitopes (class I or class II) that can also be combined. This novel approach involves the identification of different epitopes on human cells and virus antigens to induce a specific host immune response to counteract the primary host-pathogen interaction. Peptide-based vaccines have attracted rising attention due to their high safety and low development cost compared to small therapeutic molecules and antibody-based anti-viral drugs.
Advances in immunoinformatics, genetics, bioinformatics, and related sciences have facilitated the identification of different epitopes and the design of peptide-based vaccines. Using characterization techniques and web-based bioinformatics servers, researchers have identified four peptide stretches that can be used in the development of peptide-based vaccines.
In addition to peptide-based vaccines, other platforms such as DNA, mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, and protein-based vaccines are also being explored. Several vaccine candidates have shown significant promise in human clinical trials, including nucleic acid vaccines, inactivated vaccines, viral-vectored vaccines, and attenuated vaccines. However, as the number of Zika virus infections has decreased, phase III trials to assess efficacy have become more challenging.
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DNA vaccines have been used to create candidate vaccines
There is currently no vaccine to prevent or medicine to treat the Zika virus. The Zika virus, an emerging arthropod-borne flavivirus, was first isolated in Uganda in 1947 from monkeys and first detected in humans in Nigeria in 1952. Since then, interventions to reduce the burden of Zika virus infection have been mainly restricted to mosquito control, which has proved insufficient. This situation has prompted scientists to increase research on antivirals and vaccines against the virus.
The DNA vaccine platform has been used for over twenty-five years to create candidate vaccines against numerous pathogens, such as West Nile virus (WNV), Ebola virus (EBOV), dengue virus (DENV), and chikungunya virus (CHIKV). DNA vaccines are generated by cloning an antigen from a pathogen into a DNA plasmid, which is then injected. The initial safety and immunogenicity of a DNA vaccine encoding consensus Zika virus premembrane and envelope antigens delivered by electroporation have been shown to generate immune responses in mice and non-human primates. This vaccine candidate afforded complete protection against a lethal challenge of Zika.
In addition to DNA vaccines, other vaccine platforms have been evaluated for Zika, including mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, peptide and protein-based vaccines, and passive immunizations using monoclonal antibodies (MAbs). The development of peptide-based vaccines, in particular, has attracted rising attention due to their high safety and low development cost. Advances in immunoinformatics, genetics, and bioinformatics have opened new doors in vaccine design.
While there is currently no vaccine on the market, multiple organizations have initiated research initiatives to develop a safe and effective vaccine. UNICEF, in conjunction with WHO and PAHO, is working to advance R&D and address gaps in vaccine and diagnostic tools. Various Zika vaccine candidates have shown significant promise in human clinical trials, and further studies are needed to fully understand the efficacy of these vaccines in preventing congenital malformations in pregnant women.
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Inactivated vaccines have entered clinical studies
Currently, there is no vaccine or medicine to treat the Zika virus. The Zika virus was declared a Public Health Emergency of International Concern by the World Health Organization (WHO) in February 2016 due to its suspected link to birth defects. The virus has been associated with a range of congenital diseases, including microcephaly in newborns and Guillain-Barré Syndrome (GBS) in adults.
Following the 2017 Zika virus outbreak, multiple organizations initiated research efforts to develop a safe and effective vaccine. Several vaccine platforms have been evaluated, including DNA, mRNA, viral vectors, virus-like particles (VLPs), inactivated virus, live attenuated virus, peptide and protein-based vaccines, and passive immunizations using monoclonal antibodies (MAbs).
Inactivated vaccines, in particular, have shown promising results in clinical studies. Three inactivated vaccines have progressed into clinical trials, with one of them, the ZIPV vaccine, demonstrating high levels of protection against viraemia in challenges with multiple Zika strains. The ZIPV vaccine is a whole inactivated vaccine derived from the Puerto Rican strain PRVABC59. Clinical trials have shown no adverse side effects and a high seroconversion rate of 92%.
Another inactivated vaccine candidate, the purified formalin-inactivated Zika virus vaccine (ZPIV), has also demonstrated safety and immunogenicity in human clinical trials. This vaccine has induced antibody titers of ≥10 and up to over 100, indicating potential protection against the Zika virus.
While these inactivated vaccines show promising results, further clinical studies are needed to determine the precise antibody titers required for complete protection in humans. Additionally, the decreased prevalence of Zika virus infections has made it more challenging to conduct phase III trials to assess vaccine efficacy. Despite these challenges, ongoing research and collaboration between organizations such as UNICEF, WHO, and PAHO aim to expedite the development and availability of a safe and effective vaccine to prevent Zika virus infections and protect against its negative effects, especially in pregnant women and unborn children.
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UNICEF is working with WHO to advance R&D for a Zika virus vaccine
There is currently no vaccine to prevent or medicine to treat the Zika virus. The Zika virus was first isolated in Uganda in 1947 and was first detected in humans in Nigeria in 1952. Since then, interventions to reduce the burden of Zika have been mainly restricted to mosquito control, which has proved insufficient. The virus has been associated with a dramatic global burden and can cause serious birth defects.
The World Health Organization (WHO) declared Zika a Public Health Emergency of International Concern in 2016 due to its new association with microcephaly and Guillain-Barré Syndrome. In response, UNICEF is working with WHO and PAHO to advance research and development (R&D) to address gaps in vaccine and diagnostic tools. UNICEF, along with its partners, is seeking to expedite the vaccine development process to get a vaccine to market as soon as possible. The Zika vaccine project aims to support and accelerate the development and scale-up of vaccines to prevent Zika infection and disease, with a particular focus on preventing the negative effects of Zika on unborn children.
UNICEF is developing demand forecasts and specific tender criteria, which will be shared at webinars addressed to the vaccine industry. They are also planning an Advanced Purchase Commitment (APC) model to incentivize the industry and accelerate the availability of candidate vaccines. UNICEF's efforts are crucial in mobilizing industry and partners to support the development of a vaccine to protect against Zika infection.
Several vaccine candidates have shown significant promise in human clinical trials, including nucleic acid vaccines, inactivated vaccines, viral-vectored vaccines, and attenuated vaccines. A recent placebo-controlled phase I trial of a purified inactivated Zika virus vaccine candidate demonstrated safety and immunogenicity in a small number of people. In another phase 1 open-label study, the safety and immunogenicity of GLS 5700 were evaluated, with 74% of participants developing Zika-specific antibodies. Three inactivated vaccines have entered clinical studies, with no adverse side effects and high levels of seroconversion.
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Frequently asked questions
No, there is currently no vaccine to prevent Zika virus infection. However, various organizations are working to develop one.
Zika virus (ZIKV) is an arthropod-borne flavivirus of the Flaviviridae family. It was first isolated in Uganda in 1947 from monkeys and first detected in humans in Nigeria in 1952.
The Zika virus is primarily spread by the bite of an infected Aedes mosquito.
The Zika virus can cause serious birth defects, including microcephaly in newborns and Guillain-Barré syndrome (GBS) in adults.
In the absence of a vaccine, prevention of Zika virus infection focuses on avoiding mosquito bites. This includes the use of insect repellent, wearing long-sleeved shirts and pants, and staying in places with air conditioning or window and door screens.
