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Chikungunya virus and Japanese encephalitis virus
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
Japanese encephalitis is a preventable disease by vaccination. Indeed, concerted vaccination efforts in endemic countries has resulted in significant reduction in infection and therefore morbidity and mortality, but population coverage is far from complete, and vector control remains an important consideration in disease prevention. Most endemic countries in Asia use a live attenuated virus vaccine. This is given at age eight months initially, and a booster is given at the age of two. Additional boosters between the ages of six and seven are administered in some regions. In Europe, Australia, and the United States, a Vero cell-derived, inactivated virus vaccine is widely used. This vaccine is only available for those aged eighteen or greater, however, leaving children potentially vulnerable. In the United States, the mouse brain-derived vaccine that has been replaced by the Vero cell-derived vaccine remains available for children while studies on the safety of the latter are underway.
Overview of Drugs used Against Zika Virus
Published in Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay, Medicinal Chemistry of Neglected and Tropical Diseases, 2019
Sinem Ilgın, Özlem Atlı Eklioğlu, Begüm Nurpelin Sağlık, Serkan Levent
An inactivated virus vaccine is a virus that is grown in culture and then killed by methods such as heat or formaldehyde (Petrovsky and Aguilar 2014). Unlike vaccines with live attenuated viruses, inactivated vaccines negate the possibility of reactivation and replication and are thus not contraindicated in pregnant women or immunocompromised individuals. However, the attenuation also means that more immunization/boosting strategies may be required to ensure long-term protection. The need for an adjuvant might be required, but it could complicate the use of a PIV in pregnancy (Makhluf and Shresta 2018). Several PIV vaccines are under development by different study groups.
New Trends in Antiviral Therapy of CNS Infections
Published in Sunit K. Singh, Daniel Růžek, Neuroviral Infections, 2013
Currently, there are a number of ongoing clinical trials for WNV vaccines. There is an inactivated virus vaccine (Samina et al. 2005), a formalin-inactivated whole virus vaccine (Arroyo et al. 2004), a vaccine that involves the production of antigens from a heterologous virus backbone, a DNA vaccine with structural antigens being expressed from DNA plasmids (Monath et al. 2006), a DNA recombinant vaccine (Davis et al. 2001), and purified protein viral proteins (Lieberman et al. 2007). It is expected that the use of these vaccines may, in the near future, efficiently prevent this infection. Similar to WNV, an effective vaccine to prevent dengue fever has been sought. Many approaches to developing candidate vaccines have been employed. The candidates include live attenuated tetravalent vaccines, chimeric tetravalent vaccines based on attenuated dengue virus or Yellow Fever 17D, and recombinant DNA vaccines based on flavivirus and nonflavivirus vectors (Murrell et al. 2011).
Covid-19 vaccination reported side effects and hesitancy among the Syrian population: a cross-sectional study
Published in Annals of Medicine, 2023
Michel Najjar, Sara Albuaini, Mohammad Fadel, Fatema Mohsen
The cross -vaccine comparison of our study showed that viral vector-based vaccines were associated with the more frequent side effects. Our results are consistent with the findings of a German cross-sectional study [59]. A study from Algeria revealed that side effects are more prevalent among viral vector vaccines than inactivated virus vaccines [60], and this was adherent with our findings. In contrast, we found that inactivated virus vaccines were associated with lower adverse effects following vaccination. A systematic review study on the safety profile of covid-19 vaccines was showed that the low rates of local and systemic reactions were significantly lower among inactivated vaccines [61]. Inactivated virus vaccine showed higher reinfection rates after vaccination and this finding were consistent with other previous studies [62,63].
Intranasal inactivated influenza vaccines for the prevention of seasonal influenza epidemics
Published in Expert Review of Vaccines, 2018
Kaori Sano, Akira Ainai, Tadaki Suzuki, Hideki Hasegawa
Apart from intranasal split and subunit vaccines, whole virus vaccines have also been tested for intranasal administration. Human studies have shown that immunization by trivalent inactivated whole virus vaccine via the intranasal route once or twice enhanced the production of both mucosal s-IgAs and serum IgG antibodies without the use of additional mucosal adjuvants [67–69]. Safety and immunogenicity of intranasal whole inactivated virus vaccines were also observed in the elderly population [67].Unlike LAIVs, intranasal IIVs do not require infection and replication of administered vaccines to produce immune responses. Therefore, the immunogenicity of inactivated vaccines may not be easily influenced by the host’s susceptibility to influenza viruses due to the preexisting immunity, indicating that intranasal IIVs will be available to people of all ages. It was also shown in animal studies that intranasal administration of whole viruses could induce broad spectrum immune responses compared to that of subunit vaccines [70,71]. The reason for the high immunogenicity of whole virus vaccines, compared to the split and subunit vaccines, may be due to the built-in-adjuvant: viral single-stranded RNA, which is the agonist of Toll-like receptor (TLR) 7 [72–74]. Recognition of the viral RNA by TLR7 will initiate innate immune response that will be supportive in enhancing the response against vaccine administration. It has also been revealed that intranasal administration of whole inactivated viruses could induce not only mucosal s-IgA responses but also high levels of serum IgG responses. In a human study in which 50 healthy adults were enrolled, two intranasal administrations of whole inactivated virus vaccine could induce sufficient serum antibody responses that met the European Medicines Agency (EPA) criteria used for the licensure of influenza vaccines [75].
Zika virus, vaccines, and antiviral strategies
Published in Expert Review of Anti-infective Therapy, 2018
Sophie Masmejan, David Baud, Didier Musso, Alice Panchaud
Inactivated virus vaccines are produced by killed viruses, thus inactivating their pathogenicity. They offer a better safety profile than live-attenuated vaccines; however, they are less immunogenic than the latter and often require a multiple vaccine dose scheme [30]. Vaccines based on inactivated viruses were tested in four different studies. Larocca et al. used inactivated viruses and prevented viremia in vaccinated BALB/c mice [31]. Later, Abbink et al. tested the same vaccine on rhesus macaques, and confirmed these results showing that the vaccine provided neutralizing antibodies and protected from viremia after challenge with both Brazilian and Puerto Rican ZIKV strains [32]. The third study on an inactivated virus vaccine was conducted by Sumathy et al., who demonstrated that the inactivated virus vaccine conferred 100% survival, undetectable viremia after challenge, and no weight loss in AG129 vaccinated mice, compared to a control group [50]. Finally, Boigard et al. compared inactivated virus vaccine with VLP vaccine and showed that both induced neutralizing titers although the response with VLP was higher than with inactivated virus vaccine. The protective effect was not tested in this study [48]. Modjarrad et al. advanced the purified inactivated ZIKV vaccine to a phase I clinical trial. They vaccinated 67 nonpregnant participants. The vaccine appeared to be safe and well tolerated, with no systemic side effects observed. 92% of the participants had a seroconversion 6 weeks after vaccination, with antibody titers sufficiently high to attain a protective level [51]. In Modjarrad et al.’s study, the threshold for protectivity for antibody titers was set at 1:10, according to the threshold for other flaviviruses [52], although the minimal threshold for antibody titers for sufficient immunity is difficult to assess and cannot be defined based on preclinical studies. The difficulty in establishing a threshold for antibody titers to define seroconversion is due to the fact that preclinical studies (in vivo) utilize a variety of animal models as well as diverse materials such as different neutralization plaque assays, making comparisons challenging [51]. Some clinical studies of ZIKV vaccine candidates have used threshold antibody titers from preclinical studies to assess the protection against ZIKV [33,50]. Hence, it would be of great value to have a validated assay and a defined threshold of antibody titers in order to increase the validity of the future clinical studies and to allow comparison between studies. Currently, there are 4 additional ongoing phase I clinical trials with inactivated vaccines [30].