5.3.8 Other therapies
Hydrogen peroxide (H2O2) appears to be another potential therapeutic option for COVID-19. Of note, health experts have said that this compound could help prevent the virus from spreading across the body and from causing damage (Darwin Malicdem, 2020). A recent study illustrated that even just 0.5% of hydrogen peroxide could kill human coronaviruses, such as those that caused SARS and MERS (Kampf et al., 2020). Inhaling the vapor with a nebulizer has been the most convenient way to receive H2O2 to fight viral infections. The microscopic mist can easily penetrate the nostrils, sinuses, and lungs, which are commonly affected by respiratory diseases like COVID-19. Besides, molecular hydrogen has been verified to favorably modulate the generation of both O2- and NO through influencing NADPH oxidase, and the NOS enzymes (TW, LeBaron, McCullough ML, 2020). According to the National Health Commission of China, the conditional use of mixed inhalation of hydrogen and oxygen (H2/O2: 66.6%/33.3%) treatment may improve the symptoms (Sohu, 2020).
Lung transplantation can be performed in advanced patients with respiratory failure owing to COVID-19-related pulmonary fibrosis. As it is reported in a clinical study, lung transplantation may offer the ultimate treatment option for severe patients to avoid certain deaths, while at the same time protecting transplantation doctors and medical staff appropriately (Chen et al., 2020a).
Development of SARS-CoV-2 vaccines
In terms of controlling the epidemic aroused by emerging viruses, rapid diagnosis and effective vaccines serve as a complementation to antiviral therapy. Preventive and therapeutic SARS-CoV-2 vaccines will be of fundamental value as the most conspicuous way to mitigate the pandemic crisis (André, 2001). Fortunately, published data on the SARS-CoV-2 genetic sequence has sparked a global campaign to inaugurate a vaccine against the infections. The scope of the impact of the COVID-19 pandemic on humanitarianism and the economy is also prompting the assessment of the next-generation vaccine technology platform through new paradigms. On March 16, 2020, the first trial of COVID-19 vaccine candidate was launched in record speed. Moreover, the Coalition for Epidemic Preparedness Innovations (CEPI) is also combining efforts to espouse the development of vaccines against COVID-19.
As for the vaccine development of SARS-CoV-2, the pivotal and tangible avenues can be divided into four aspects: 1) Selection of antigen epitope. 2) Overcoming the antibody-dependent enhancement (ADE) issue. 3) Weighing humoral immunity and cellular immunity. 4) Selection of technical route befittingly. Up till now, structural epitope mapping by homology modeling has uncovered the immunoreactive antigen epitopes of SARS-CoV-2 (Tilocca et al., 2020). The mainstream of the vaccine development is based upon the S protein in virtue of its essential role in the viral infectivity. Other subsequent developments can constrain focus on other viral proteins (i.e., the N protein, and E protein). Further, the titers of neutralizing antibodies that were variable among different patients were associated with the spike-binding Abs targeting S1, RBD, and S2 regions (Wu et al., 2020a). In this regard, we should also pay more attention to the titers of neutralizing antibodies.
In addition, researchers need to know whether the vaccine will induce the same type of immune system failures that have been observed previously. In some cases, the vaccine-primed immune system seems to initiate a shoddy response to natural infections (Peeples, 2020). Additionally, allergic inflammation aroused by Th2 immunopathology should be taken into consideration, according to the coronavirus experts (Peeples, 2020). Therefore, animal and human clinical trials of COVID-19 candidate vaccines should encompass a rigorous assessment of possible immune complications before putting into use.
According to the previous study on SARS-CoV, SARS-specific IgG Ab may ultimately fade away, and the peripheral memory B cell response cannot be detected in recovered SARS patients. In stark contrast, the memory response of specific T cells lasted at least six years, implicating the significance of cellular immunity for preventing the recurrence epidemics (Tang et al., 2011).
With regard to the technical routes, we can see efforts to espouse ‘quick-fix’ programs for the purpose of developing vaccines against COVID-19 worldwide (Jiang, 2020). There is a desperate need for selecting effective technical routes to develop different kinds of vaccines (i.e., live-attenuated vaccines, inactivated vaccines, nucleic acid vaccines, subunit, recombinant, polysaccharide, and conjugate vaccines) in a quicker and safer manner (HHS.gov, 2020).
As announced by the WHO, there are now more than 70 potential vaccines under development, with three already in clinical trials (Keown, 2020). The following section will describe the status of vaccine development against this crisis by miscellaneous methods. The potential vaccine candidates for COVID-19 are summarized in Table 2.
Table 2. The potential vaccine candidates for COVID-19 (Le et al., 2020; Hodgson, 2020; Times, 2020; ARENA, 2020; ChiCTR, 2020).