Emerging variants of the virus that causes Covid-19 have triggered concern that vaccines developed so far do not provide the high level of protection seen in clinical trials. Variants have been identified referring to California, South Africa, Brazil and the United Kingdom.
But not all variants need a new vaccine, as vaccines produce a broad immune response that will likely cover many mutations. This is what needs to be done to assess whether a vaccine needs to be modified and how it can be modified.
Detection To deal with a new variant, it must first be detected. Surveillance is key, so scientists need to be constantly monitored and involved in international cooperation, just as they do for the flu virus. Approved vaccine manufacturers, including Pfizer / BioNTech, Moderna and Oxford / AstraZeneca, are looking for ways to improve their vaccines so they are prepared for any variant.
Comparison Once a variant of concern has been identified, scientists need to check whether the effectiveness of the existing vaccine has decreased significantly. In the case of the variant discovered in the UK, scientists were confident that the vaccines already available worked well against it, but for the discovery in South Africa the data are much less encouraging.
Modification If a vaccine modification is needed, the technology used in the vaccine determines the speed and ease of the modification. For example, mRNA vaccines manufactured by Pfizer / BioNTech and Moderna are much easier to modify than traditional vaccine technologies.
Graph 1
Graph 2
Production BioNTech has said it can produce a new vaccine within six weeks of decision-making. But the Oxford / AstraZeneca team, which uses more traditional viral vector technology, says that while it may produce a new formulation in days, it takes much longer to produce. He hopes to have a vaccine designed for the variant discovered in South Africa ready for the fall.
Tests It is not clear to what extent the modified vaccine trials should be. In the case of influenza vaccines, regulators do not require large-scale testing, but are satisfied with minor studies showing that they work as well as the original vaccine. This is probably what is expected of Covid-19 vaccine manufacturers.
Approval Regulators will have to approve the new vaccine. In the UK, the Medicines and Health Products Regulatory Agency (MHRA) has said it is in talks with vaccine manufacturers about the re-approval process. “We can say at this stage that a full approval process is unlikely to be necessary,” a spokesman said last month. “No vaccine will be authorized for supply in the UK unless the expected standards of safety, quality and effectiveness are met.”