Figure 1
Landscape of COVID-19 vaccines. (A) Several vaccines are in the production pipeline at several development stages. (B) Although different approaches are being employed in the development of COVID-19 vaccines, many of the vaccines currently undergoing clinical trials are subunit and vector-based vaccines. (C) The global distribution of COVID-19 vaccine recipients as at 22 February 2021. Data source: Covid-19 Vaccine Tracker Updates: The Latest – The New York Times (nytimes.com); COVID19 Vaccine Tracker (trackvaccines.org); https://ourworldindata.org/covid-vaccinations.
Table 1
COVID-19 vaccine types, mechanisms, and features.
| Vaccine type | Mechanism of action | Advantages | Disadvantages |
|---|---|---|---|
| Live attenuated | Produce by growing the virus in unfavourable conditions or by generating a genetically weakened version of the virus. | (1) Relatively higher efficacy than inactivated vaccines. (2) Immune response is directed against many SARS-CoV-2 antigens. | (1) Production and handling are associated with major biosafety risks. (2) May be unsuitable for use in some age groups. |
| Inactivated | SARS-CoV-2 is inactivated by exploiting different chemical techniques to produce a vaccine. | (1) More stable than live attenuated vaccines. (2) Immune response is directed against many SARS-CoV-2 antigens. | (1) Short duration of immune memory which demands inoculation of higher vaccine doses. (2) May result in hypersensitivity. |
| Subunit | The S protein or its fragments are produced by rDNA technology to make a vaccine. | (1) Elicit robust immune response, when combined with adjuvants. | (1) Require stringent downstream purification steps which are often expensive. |
| DNA-based | DNA plasmids are used to induce cells to produce the S protein, thus activating an immune response. | (1) Great flexibility for manipulation of the coded antigen. (2) Quick to produce. (3) High antibody titres. | (1) Specialized and complex delivery (electroporation). (2) Repeated doses may cause toxicity. (3) Relatively lower immune responses. |
| mRNA | mRNA vaccines temporarily induce cells to produce the antigen protein encoded. | (1) Low production costs. (2) Quick to produce. | (1) Vaccine preparations must be kept at ultralow temperatures. |
| Vector | DNA coding for the S protein is conveyed into cells by viral vectors. By inserting the DNA in a virus, it is possible to exploit the virus’s great ability to infect and deliver the mRNA into the human cells. | (1) Candidate vaccines may induce a mucosal immunity capable of neutralizing the virus, thus inhibiting its ability to enter the human body. | (1) Possibility of presenting varied immune responses. |
Table 2
List of all 12 vaccines currently approved by at least one country (Date: 28 February 2021).
| Developer | Name | Type | Countries in use | Immunogenic features | Efficacy |
|---|---|---|---|---|---|
| FBRI/Novavax | EpiVacCorona | Protein | 01 | High levels of S-specific neutralizing antibodies. | Not available |
| Pfizer/BioNTech | BNT162b2 | mRNA | 65 | 2 repeated doses (28 days apart) which induce elevated concentrations of neutralizing antibody titers. Also induce CD4+ and CD8+ T cells responses. | 95% |
| Moderna | mRNA-1273 | mRNA | 40 | 2 repeated doses (28 days apart) which induce neutralizing antibodies and CD4+ and CD8+ T cell responses. | 94.1% |
| Janssen (Johnson & Johnson) | Ad26.COV2.S | Vector | 1 | Single dose vaccine inducing neutralizing antibodies. | 85% |
| CanSino | Ad5-nCoV | Vector | 3 | Strong immune response with single delivery but impeded due to pre-existing immunity. | 65.7% |
| Gamaleya | Sputnik V | Vector | 38 | Induces high neutralizing antibody titers. Also induces CD4+ and CD8+ T cells responses. | 91.4% |
| Oxford/Astra Zeneca | AZD1222 | Vector | 56 | Strong immune response and high neutralizing antibodies with single injection (Low pre-existing immunity). | 62% |
| Serum Institute of India | Covishield | Vector | 13 | Oxford-AstraZeneca vaccine is being manufactured locally by the Serum Institute of India | Similar to Oxford/Astra Zeneca |
| Bharat Biotech | Covaxin | Inactivated | 2 | N/A | 81% |
| Sinopharm (Wuhan) | Vero Cells | Inactivated | 2 | Enhanced induction of neutralizing antibodies and enhanced immunogenicity. | 79% |
| Sinovac | CoronaVac | Inactivated | 12 | Elevated induction of neutralizing antibodies and enhanced immunogenicity. | 50-91%* |
| Sinopharm (Beijing) | BBIBP-CorV | Inactivated | 16 | Safe and high antibody titers. | 79-86%* |
[i] * variations in results obtained in different trials.
Data retrieved from the COVID19 vaccine tracker of scientists of McGill University, Canada, accessed on 28 February 2021 (https://covid19.trackvaccines.org/vaccines).
Figure 2
Distribution of CVD risk factors in COVID-19 mortality. (A) CVD and hypertension are responsible for most of COVID-19 related mortalities. (B) Hypertension is a major contributor to COVID-19 mortality. Data sourced from study by Li et al., 2020 [19].
Figure 3
Outcomes of COVID-19 infection in CVD patients.