**2.5 Evaluation of plant-based vaccines side effect**

Vital part of vaccine research is the risk assessment through randomized, double-blind placebo-controlled multicentre trials. Vaccine side effects can be evaluated under two categories as common side effects (high fever, vomiting, dizziness, anxiety and nausea) and rare side effects (risk of hospitalization, death or long-term morbidity). Same evaluation processes is required for plant-based vaccines as all traditional and recombinant vaccines. In literature, there are various studies in emphasis to safety and side effects of plant-based vaccines.

Plant-based vaccines can be evaluated in two different ways: cases in which the plant content is directly applied in pure form and the cases where the vaccine content is isolated and mixed with adjuvant. Phase studies were initiated for many candidate vaccines, where antigen or VLP was produced and then mixed with adjuvant before injection. In reported Phase I vaccine case against influenza A presented common side effects on volunteers as high fever, vomiting, dizziness, anxiety and nausea [96]. Similarly, in another case local effects occurred in the vaccination area and 93% of side effects were mild effects [98]. McCormick et al., stated in their studies that volunteers showed symptoms that were described as severe at a very low rate, but recovered within 1–2 days without the need for medical intervention, and the vaccine candidate was quite safe [99]. Moreover, Pillet et al. tested the vaccines with 300 healthy adults and 450 volunteers over the age of 50 in their phase III study on two different age groups. As a result, a higher rate of fatigue was observed in volunteers over 50 years old [100]. Ward et al. reported that the most common side effect was pain at the injection site in their studies on 22,854 volunteers and mortality rate was slightly higher for inactivated.

vaccine comparing to virus like particles [101]. Chichester et al., (2018) reported that 94% of the volunteers developed at least one of the side effects of high fever, vomiting, dizziness, anxiety and nausea [102]. In all of these studies with both oral and injectable vaccines, the observed effects were evaluated as mild to moderate. In this way, plant-based production has been defined as an effective and safe vaccine production tool [103]. Production of the adjuvants to be used to stimulate mucosal and peripheral immunity in the plant or the selection of plant which produce appropriate secondary metabolites that can act as mucosal adjuvants contributes to the decrease in the incidence of side effects. The number of studies in which plant-based vaccine candidates have passed to phase studies were much less than classical vaccine studies. When these studies are evaluated, there is no significantly increased side effect risk report concerning plant-based vaccines against any other vaccines production options [104].

#### **2.6 Legal regulations involving plant-made pharmaceuticals**

Regulatory processes of the vaccine development, approval, authorization, licensing, distribution, and marketing are as challenging as the production. There are both national and centralized regulatory agencies. These agencies emphasize on scientific evaluation of data, quality of the product, safety for human use, verification of reported efficacy and authenticity of product labels. In USA, centralized regulatory agency is Food and Drug Administration known as FDA. As plant based-vaccines are considered in biological materials apart from chemical entities, plant-made pharmaceutics are regulated under Biologics License Application (BLA) [105]. The European Union (EU) members have both their own national regulation and the centralized regulation under European Medicines Agency (EMA) which acts as the counterpart of FDA in Europe. The Committee on Herbal Medicinal Products (HMPC) is the EMA's committee responsible for compiling and assessing scientific data on herbal substances, preparations and combinations, to support the harmonization of the European market [106]. However, considering the nature of plant based vaccines, they are under authorization of The Committee for Medical Products for Human Use (CHMP) which plays a vital role in the authorization of medicines in the European Union (EU).

Strictness of the regulation is mostly based on the production method and the host plant. Non-food plants as *Nicotiana* species and the controlled indoor production methods as plant tissue cultures or climate rooms are not regulated as strictly as in field production of GM food plants. However, there are opinion differences between EU and USA regarding the plant-made PMPs. In USA, regulation is at product level. Field use of GM plants and plants used in vaccine development are under secondary regulation of United States Department of Agriculture (USDA). In May, 2020 USDA Animal and Plant Health Inspection Service (APHIS) released revision on 7 Code of Federal Regulation (CFR) Part 340 regulations (85 Fed. Reg. 29790) which regulates the importation, interstate movement, and environmental release of genetically engineered organisms that are or may be plant pests [107]. Therefore, scrutiny on biotechnological production is further reduced in favor of researchers and companies. PMPs are currently under regulation of Title 21 (Food and Drugs) US CFR along with other traditionally produced counterparts. In EU regulation is on both production and final product level. All GM plant derived pharmaceuticals including plant based vaccines are under the same regulation of other biotechnology derived drugs which is indicated in European Commission Directive 2001/83/EC (on the Community code relating to medicinal products for human use) [108] and Regulation No 726/2004 (for the authorization and supervision of medicinal products for human and veterinary use) [109]. Also, if the host plant is a human food or animal feed source, cultivation and release of GM plant is under regulation of EC Directive 2001/18/EC (on the deliberate release into the environment of genetically modified organisms) [110] and 1829/2003/EC (on genetically modified food and feed).

Regulatory approval of a PMPs and other biotechnologically derived products may take up to a year depending on the legal response limits of the regulation agencies. However, Covid-19 pandemic triggered a realization on EU and UK for national and global needs. Therefore, product review, conditional approval and deployment timelines are significantly reduced for PMPs [111].

In conclusion, infectious diseases threatened humanity countless times throughout history. In particular, as pandemic and epidemic diseases killed millions of people, it increases in importance to develop safe and cost-effective vaccines and their storage and rapid distribution. Apart from many diseases such as diphtheria, cholera, typhoid, tuberculosis, which are controlled by vaccine campaigns in

### *Plant-based Vaccines: The Future of Preventive Healthcare? DOI: http://dx.doi.org/10.5772/intechopen.97861*

developed countries, new vaccine production systems using recombinant DNA technologies are needed for emerging diseases such as COVID-19, MERS-CoV, avian influenza, Ebola, Zika and possible future infections. Plant-based vaccine production for humans and animals stands out as an important alternative that can be used to overcome the disadvantages of existing conventional vaccines. Within the scope of plant biotechnology, it became possible to produce cost-effective, immunogenic and safe vaccines thanks to the development of gene transfer strategies to plants and improvements in amount, isolation and purification and addition of adjuvant for production of recombinant vaccine antigens in plants. It is an undeniable fact that the possibilities that recombinant vaccines can offer us will increase with new standards and legal regulations to be introduced for the development, approval, authorization, licensing, distribution and marketing of such vaccines. In scope of future preventive healthcare, it is hard to assume monopoly of one particular vaccine technology. There will always be some ups and downs in any vaccine production methods. However, plant based vaccines represent considerable strong suits and offer swift and viable solutions over traditional and other recombinant vaccines.
