The SMC has collated resources related to COVID-19 vaccine development.
First published 13 May 2020
Resources
A list of trusted information on Covid-19 vaccines from the office of NZ’s Prime Minister’s Chief Science Advisor. 23 Feb 2021
Australia’s Rapid Research Information Forum: The most promising vaccines for COVID-19
StatNews has been tracking the development of vaccines.
The case for New Zealand to have its own COVID-19 vaccine programme (New Zealand Medical Journal) 24 April 2020
Australian SMC briefings
7 May 2020: Researchers crack code behind historic success of TB vaccine now being trialled for COVID-19
2 April 2020: CSIRO starts testing COVID-19 vaccines
Vaccines under development for COVID-19
Vaccines are designed to stimulate the body’s immune system to better fight infections or diseases.
There are 4 main types of vaccines currently in use:
- Live-attenuated vaccines
- Inactivated vaccines
- Subunit, recombinant, polysaccharide, and conjugate vaccines
- Toxoid vaccines
Live-attenuated vaccines used weakened versions of the virus or bacteria causing the disease. Because of their similarity to the pathogen they often stimulate a very strong and long-lasting immune response. Examples include the measles, mumps & rubella (MMR) combined vaccine, and the smallpox vaccine.
Inactivated vaccines use dead or non-reproducing versions of the pathogen. They tend to provide weaker or shorter-term immunity, so booster shots may be needed. Examples include flu, hepatitis A, and rabies vaccines.
Subunit, recombinant, polysaccharide, and conjugate vaccines use specific pieces of the pathogen — such as proteins on the virus surface. Their specificity provides a very strong immune response, and can be used on people with a weakened immune system. Booster shots may be required. Examples include Hepatitis B, Meningococcal disease, and the Human Papillomavirus vaccines.
Toxoid vaccines use a toxin produced by the pathogen. Booster shots may be required. Examples are Tetanus and Diphtheria vaccines.
New types of vaccines being developed
More recent vaccine types are:
- DNA vaccines
- RNA vaccines
- Recombinant viral vector vaccines
DNA vaccines include the sequence of an antigen into a circular DNA plasmid to stimulate an immune response. They can also include other additives that help the vaccine enter or target cells, or other immunity. DNA vaccines are theoretically easy to produce and inexpensive, but yet to be fully tested. DNA vaccines were developed for SARS, H5N1 influenza and the Zika virus, but clinical trials were not completed due to these epidemics ending.
RNA vaccines use a linear strand of messenger RNA (normally produced in cells to make a protein) that contains the desired antigen. When it enters a cell it will produce the antigen and stimulate the immune system. RNA vaccines could be injected or given as an oral spray. No RNA vaccines are approved for human use, though trials are underway both for infectious diseases (Ebola, and H1N1 influenza) and specific cancers.
Recombinant viral vector vaccines are modified viruses that can produce the desired antigen for a specific disease. The virus is used to deliver the antigen to the appropriate places. These type of vaccines may be referred to as “minigenes” (although that term can also be applied to DNA vaccines). Recombinant vector vaccines have been approved for veterinary uses. For example, rabies and distemper. There is research into using such vaccines for HIV, Ebola, and the Zika virus.
Covid-19 vaccines in development
As at 11 May eight vaccines are registered with the WHO as being in the early stages of clinical trials, with 102 other potential vaccine candidates in pre-clinical evaluation. Other clinical trials are reported by the US ClinicalTrials.gov, and the European Union Clinical Trials Register. The vaccines currently in clinical trial involve Inactivated virus, DNA, RNA and Recombinant viral vaccines.