Three main types of vaccines have so far been used in the fight against Covid-19 around the world, but more are in trials and under development.
ADENOVIRUS VECTOR VACCINES
This type includes AstraZeneca, and uses a modified adenovirus to deliver DNA coded with a SARS‑CoV‑2 protein to spark the body’s immune system into action. A similar mechanism is also used in the Russian Sputnik V and Chinese Convidecia vaccines which have been rolled out in China, Russia, Mexico, Brazil, Argentina, Chile, Ecuador, Moldova, Belarus, Hungary, Serbia, Pakistan, the Philippines, Indonesia, Malaysia and the United Arab Emirates. The US-made Johnson & Johnson jab is also the same type but was initially only a single-dose vaccine, until US authorities recommended a second booster shot in October 2021.
The two other vaccines currently approved in Australia – Pfizer and Moderna – both use this platform to deliver Covid-19 immunity. Both contain RNA or messenger RNA in a drop of fat which then causes some cells to develop a harmless version of the SARS-CoV-2 spike protein to kickstart the body’s resistance to the disease. Side effects are very rare but the vaccine needs to be stored at a very low temperature, which causes distribution challenges, especially in third world countries. A freeze-dried version is currently under development which would not need to be kept cold. It has been approved and used throughout the world except for a handful of countries including Russia and China.
INACTIVATED VIRUS VACCINES
These are more traditional forms of vaccines which take laboratory-cultivated Covid-19 virus particles and kill them with heat or formaldehyde but still retain the proteins needed to create an immune response when injected. It is the same type of technology that was used in the 19th and 20th century against cholera, plague, typhoid and rabies. It’s the mechanism behind the Chinese CoronaVac/Sinovac, BIBP and WIBP vaccines, India’s Covaxin, Russia’s Covivac, Kazakhstani QazVac, and Iran’s COVIran Barekat.
Often known as protein vaccines, this a controversial new technology which just uses a small piece of protein to create the immune response. Critics claim the proteins may be too small to be recognised by the human immune system. The vaccines are largely still in testing, but Russia has authorised its EpiVacCorona for use, along with Turkmenistan. China, Uzbekistan, Indonesia and Malaysia are also using a Chinese version, ZF2001. The US-produced Covovax has been undergoing trials in Australia, Mexico and India and has been authorised in Indonesia and the Philippines.
These nasal spray vaccines are the holy grail against Covid – easy to distribute and easy to use, with no needle fear. So far there are no nasal spray vaccines for Covid-19, but there is one for the flu – brand-name FluMist in the US and FluEnz in Europe – which may see a Covid version developed eventually.
New technologies that are being developed that could be used in the fight against Covid include virus-like particles, which mimic the virus without including any virus material, DNA vaccines which uses genetically modified cells to re-write the body’s blueprint to fight the disease, lentivirus vaccines which inject new genes into the body to make it immune, conjugate vaccines which is a two-pronged varied of protein vaccines, and using a harmless variant of the rabies virus vesicular stomatitist – currently used as a ‘trojan horse virus’ to help fight AIDS – which also carries the Covid-19 spike protein.