7 most common COVID-19 vaccines
| COVID-19 vaccines | Pfizer-BioNTech BNT162b2 | Moderna mRNA-1273 | Sinovac-CoronaVac | Sinopharm BBIBP | Bharat Biotech BBV152 Covaxin | Oxford/AstraZeneca ChAdOx1-S [recombinant] | Janssen (Johnson & Johnson) Ad26.COV2.S |
| Age recommendation | ≥5 years old | ≥12 years old | ≥18 years old | ≥18 years old | ≥15 years old | ≥18 years old | ≥18 years old |
| Type of vaccine | mRNA | Inactivated virus | Viral vector | ||||
| Booster dose* | ≥18 years old
12-17 years old |
≥18 years old | – | – | – | – | ≥18 years old |
| Number of countries | 151 | 86 | 47 | 88 | 9 | 184 | 80 |
*Most countries have recommended the use of Pfizer-BioNTech and Moderna as booster shots.
How does each vaccine type differ?
mRNA vaccines
The mRNA COVID-19 vaccines, short for messenger ribonucleic acid, contains single DNA strands that allow the body to transcribe viral proteins. The body’s immune system will recognise the viral particle as foreign material and produce antibodies against it. Specifically for the SARS-CoV-2 virus, the pronounced “spike proteins” feature is what the antibodies target.
Inactivated virus vaccines
Vaccines made from inactivated viruses contain dead pathogens. The genetic materials are removed, via chemical, heat, radiation agents, leaving the virus shell behind. Thereafter, the body will detect the antigens on the inactivated virus and trigger the immune system to destroy it.
Viral vector
Viral vector vaccines are designed to function like delivery vehicles. A harmless virus is used as a medium to introduce a genetic code. Oxford/AstraZeneca’s COVID vaccine is one such example, using the chimpanzee adenovirus vector to pass on the instructions of making the spike proteins.
All vaccines aim to retain immunogenicity in the body. Thus, should an individual get infected by the virus, their symptoms would be less severe.
Effectiveness of booster shots against Omicron
The highly mutated and infectious coronavirus strain, Omicron, is constantly uncovering itself in many cities. In addition, studies have shown that waning of vaccine protection against the coronavirus begins one month after the second dose and accelerates in the next few months. A third round of vaccination could be the key to better protect one against COVID.
Research have been conducted for certain vaccines to test for the neutralisation efficiency as booster vaccines. AstraZeneca reported the use of Vaxzevira as a third booster in neutralising the Omicron variant to be as effective as getting a second dose against the Delta variant. Professor Sir John Bell, Regius, one of the study investigators, said: “These results support the use of third dose boosters as part of national vaccine strategies, especially to limit the spread of variants of concern, including Omicron.”
Currently, the WHO website states that COVID vaccines Pfizer-BioNTech, Moderna, and Janssen have been authorised as booster vaccines as well.
Various countries, including Singapore, have also begun rolling out booster shot programmes incorporating heterologous boosting. Indonesia has also started The Health Ministry-run booster programme on 12 January 2022 with the 5 approved COVID vaccines – Sinovac, Pfizer, AstraZeneca, Moderna, and Zifivax.
Vaccination in children above five
Paediatric primary series vaccination has already been in place in a few countries including China and Cambodia and Singapore. According to CNBC, Hong Kong will also commence vaccination for children ages five and older. Chief Executive Carrie Lam said, “Children over five will be able to get the Chinese-made Sinovac vaccine”. As of now, there are no reports of adverse reactions in vaccinated children.
Information in this article is accurate as of 21 Jan 2022.
