COVID-19 Vaccine Candidates

COVID-19, the disease caused by the coronavirus named SARS-CoV-2, first identified in Wuhan, China in December 2019 has spread globally, resulting in the ongoing 2019-2020 coronavirus pandemic. This disease is spread by the release of aerosol droplets that can be transmitted via person-to-person if they are within two meters of an infected person for 15 minutes or longer. The most common symptoms of coronavirus are fever, cough, shortness and breath or breathing difficulties. In more severe cases, pneumonia or severe acute respiratory syndrome may occur and these cases require hospitalisation.

The preventative measures to reduce transmission of the virus are social distancing and practising good hygiene. However, these measures only work to slow the spread of the virus, but do not provide complete immunity against the coronavirus.There is no treatment for COVID-19, there are only pain-reducing medications such as ibuprofen and in more severe cases, the use of ventilators and supply of oxygen.

Currently, many pharmaceutical companies around the world are developing coronavirus vaccines for COVID-19 (cov 19 vaccine). According to the World Health Organisation (WHO), there are currently over 40 vaccines in development against COVID-19.

A vaccine is a biological preparation that contains an agent that resembles a disease-causing microorganism such as a virus or bacteria. Vaccines are often made from weakened or killed forms of the microbe, one of its surface proteins or the toxin that the microbe produces. The vaccine serves to stimulate the immune system to produce antibodies against the infectious agent, thereby providing immunity to the microbe in the future.  

The major coronavirus vaccine types that pharmaceutical companies are developing currently for the treatment of COVID-19 are DNA- and RNA based vaccines, non-replicating viral vector vaccines, inactivated virus vaccines, live attenuated virus vaccines and protein subunit vaccines.

DNA Based COVID-19 Vaccines: These types of vaccines use the DNA of SARS-CoV-2 expressed in a plasmid. Once it is injected into the body, the host immune system recognises the foreign viral DNA and elicits an immune response against it.

RNA Based COVID-19 Vaccines: Similarly to DNA vaccines, these use RNA of SARS-CoV-2 to be injected into the host. The form of RNA is often mRNA, as this can be translated into viral proteins and recognised by the host.

Non-Replicating Viral Vector: These vaccines use a well-established inactivated or killed viral vector such as adenovirus to express proteins of SARS-CoV-2 so that the proteins can be recognised by the immune system to elicit an immune response.

Inactivated Virus: These vaccines are composed certain proteins or components of the virus to elicit an immune response. In order to stimulate a stronger immune response, an adjuvant such as alum is often added.

Live Attenuated Vaccine: These vaccines are composed of the whole virus, however the infectivity of the virus has been weakened so that it can replicate and stimulate an immune response but it does not cause illness.

Protein Subunit Vaccine: This type of vaccine is composed of fragments of the virus, which triggers an immune response without exposing the body to the whole virus.

A list of vaccine candidates currently being developed for COVID-19 are listed below.

VLP - virus-like particle

MVA- Modified Vaccinia Ankara (attenuated vaccine of a poxvirus)

RBD - Receptor Binding Domain

LNP- Lipid Nanopaticle