COVID-19 vaccines

A COVID‑19 vaccine is a vaccine intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), the virus that causes coronavirus disease 2019 (COVID‑19). Prior to the COVID‑19 pandemic, an established body of knowledge existed about the structure and function of coronaviruses causing diseases like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). This knowledge accelerated the development of various vaccine platforms during early 2020. The initial focus of SARS-CoV-2 vaccines was on preventing symptomatic, often severe illness. On 10 January 2020, the SARS-CoV-2 genetic sequence data was shared through GISAID, and by 19 March, the global pharmaceutical industry announced a major commitment to address COVID-19. The COVID‑19 vaccines are widely credited for their role in reducing the spread, severity, and death caused by COVID-19.

Many countries have implemented phased distribution plans that prioritize those at highest risk of complications, such as the elderly, and those at high risk of exposure and transmission, such as healthcare workers.

As of 18 September 2021, 5.92 billion doses of COVID‑19 vaccines have been administered worldwide based on official reports from national public health agencies. AstraZeneca anticipates producing 3 billion doses in 2021, Pfizer–BioNTech 1.3 billion doses, and Sputnik V, Sinopharm, Sinovac, and Janssen 1 billion doses each. Moderna targets producing 600 million doses and Convidecia 500 million doses in 2021. By December 2020, more than 10 billion vaccine doses had been preordered by countries, with about half of the doses purchased by high-income countries comprising 14% of the world’s population.

Vaccine types

Vaccine platforms being employed for SARS-CoV-2. Whole virus vaccines include both attenuated and inactivated forms of the virus. Protein and peptide subunit vaccines are usually combined with an adjuvant in order to enhance immunogenicity. The main emphasis in SARS-CoV-2 vaccine development has been on using the whole spike protein in its trimeric form, or components of it, such as the RBD region. Multiple non-replicating viral vector vaccines have been developed, particularly focused on adenovirus, while there has been less emphasis on the replicating viral vector constructs.

At least nine different technology platforms are under research and development to create an effective vaccine against COVID‑19. Most of the platforms of vaccine candidates in clinical trials are focused on the coronavirus spike protein and its variants as the primary antigen of COVID‑19 infection,, since the S protein triggers immune responses. Platforms being developed in 2020 involved nucleic acid technologies (nucleoside-modified messenger RNA and DNA), non-replicating viral vectors, peptides, recombinant proteins, live attenuated viruses, and inactivated viruses.

Many vaccine technologies being developed for COVID‑19 are not like vaccines already in use to prevent influenza, but rather are using “next-generation” strategies for precise targeting of COVID‑19 infection mechanisms. Several of the synthetic vaccines use a 2P mutation to lock the spike protein into its prefusion configuration, stimulating an adaptive immune response to the virus before it attaches to a human cell. Vaccine platforms in development may improve flexibility for antigen manipulation, and effectiveness for targeting mechanisms of COVID‑19 infection in susceptible population subgroups, such as healthcare workers, the elderly, children, pregnant women, and people with weakened immune systems.

RNA vaccines

Diagram of the operation of an RNA vaccine. Messenger RNA contained in the vaccine enters cells and is translated into foreign proteins, which trigger an immune response.

Several COVID-19 vaccines, including the Pfizer–BioNTech and Moderna vaccines, have been developed to use RNA to stimulate an immune response. When introduced into human tissue, the RNA contained in the vaccine acts as messenger RNA (mRNA) to cause cells to build the SARS-CoV-2 spike protein. This teaches the body how to identify and destroy the corresponding pathogen. RNA vaccines often, but not always, use nucleoside-modified messenger RNA. The delivery of mRNA is achieved by a coformulation of the molecule into lipid nanoparticles which protect the RNA strands and help their absorption into the cells.

RNA vaccines were the first COVID‑19 vaccines to be authorized in the United Kingdom, the United States and the European Union. Authorized vaccines of this type are the Pfizer–BioNTech and Moderna vaccines. The CVnCoV RNA vaccine from CureVac failed in clinical trails.

Adenovirus vector vaccines

These vaccines are examples of non-replicating viral vector vaccines, using an adenovirus shell containing DNA that encodes a SARS‑CoV‑2 protein. The viral vector-based vaccines against COVID‑19 are non-replicating, meaning that they do not make new virus particles, but rather produce only the antigen which elicits a systemic immune response.

Authorized vaccines of this type are the Oxford–AstraZeneca COVID-19 vaccine, the Sputnik V COVID-19 vaccine, Convidecia, and the Janssen COVID-19 vaccine.

Convidecia and the Janssen COVID-19 vaccine are both one-shot vaccines which offer less complicated logistics and can be stored under ordinary refrigeration for several months.

Sputnik V uses Ad26 for its first dose, which is the same as Janssen‘s only dose, and Ad5 for the second dose, which is the same as Convidecia‘s only dose.

On 11 August 2021, the developers of Sputnik V proposed, in view of the Delta case surge that Pfizer test the Ad26 component (termed its ‘Light’ version) as a booster shot.

Inactivated virus vaccines

Inactivated vaccines consist of virus particles that have been grown in culture and then are killed using a method such as heat or formaldehyde to lose disease producing capacity, while still stimulating an immune response.

Authorized vaccines of this type are the Chinese CoronaVac, BBIBP-CorV, and WIBP-CorV; the Indian Covaxin; later this year the Russian CoviVac; the Kazakhstani vaccine QazVac; and the Iranian COVIran Barekat. Vaccines in clinical trials include the Valneva COVID-19 vaccine.

Subunit vaccines

Subunit vaccines present one or more antigens without introducing whole pathogen particles. The antigens involved are often protein subunits, but can be any molecule that is a fragment of the pathogen.

The three authorized vaccines of this type are the peptide vaccine EpiVacCorona, ZF2001, and MVC-COV1901. Vaccines with pending authorizations include the Novavax COVID-19 vaccine, Soberana 02 (a conjugate vaccine), and the Sanofi–GSK vaccine.

The V451 vaccine was previously in clinical trials, which were terminated because it was found that the vaccine may potentially cause incorrect results for subsequent HIV testing.

Our company is cooperating with main COVID-19 vaccines manufactures and distributors and can offer to our customers next vaccines: Comirnaty (Pfizer), Vaxzevria (AstraZeneca), Spikevax (Moderna), EpiVacCorona (Vector, Russia), Sputnik-V and Sputnik-L (Gamaleya Research Institute of Epidemiology and Microbiology in Russia).