“Reinfection in vaccinated people needs to be analysed based on severity”

May 8, 2021 0 By S Harachand

Professor Shabir A Madhi is Professor of Vaccinology and Dean: Faculty of Health Sciences, University of the Witwatersrand, Johannesburg.

He is also director of Vaccines & Infectious Diseases Analytics Research Unit (Wits-VIDA) and co-director of African Leadership in Vaccinology Expertise (ALIVE).

In a conversation with Future Medicine, Dr Madhi says he expects the next generation of vaccines that can offer a higher level of protection against all variants of SARS-CoV-2 to become available soon — probably by the 3rd quarter of 2021.

Edited excerpts:

Cases of reinfection have been reported in fully vaccinated people in many places. What shall be the possible reasons for this, since SARS-CoV-2 strains that are resistant to the current vaccines are still to emerge?

Past infection offers close to 85% protection against reinfection due to the ancestral virus. Also, reinfection in vaccinated people needs to be analysed based on severity. Not all the vaccines will protect against mild infection. However, they are likely to be more consistent in protecting against severe disease.

None of the currently authorised vaccines offer adequate protection against the B.1.351 variant, despite most of them showing some efficacy on other known variants, including the B.1.1.7 lineage. What is it that makes the South African variant a challenge to the existing array of vaccines?

The B.1351 variant has additional mutations of the RBD and NTD of the spike protein, which are targets of the neutralising antibody, rendering it relatively resistant to antibody activity induced by past infection with the ancestry virus as well as antibodies induced by 1st generation COVID-19 vaccines. It is, however, possible that protection for mild and moderate disease (upper airway infection) is more affected than severe COVID-19 (lower airway infection), as T cell immunity may play a more important role in protecting against lower airway disease. The breadth of T cell responses is less affected by the mutations as opposed to the antibody responses.

How far does the global spread of the B.1.351 variant impact the efforts to rein in the pandemic with the scaling up of vaccination?

It depends on to what extent it seeds. Also, there are other similar variants that are being identified globally. Overtime, as vaccines are rolled out — especially if there is a very sluggish rollout, one can expect further mutations to emerge if the virus continues transmitting at moderate levels.

Looking at current development pipelines, do you think next-generation vaccines targeting the mutant variants could take at least a year to reach, especially in the developing world?

I expect that next generation vaccines will become available sooner — probably by the third quarter of 2021. Even though the current generation of vaccines might be compromised in protecting against mild disease, it is very likely that they will retain high levels of protection against severe disease, even against the B.1351 variant, as has been seen for J&J (82% protection) and Novavax vaccine (100% protection) in SA against B.1351. We need to recalibrate expectations from first generation COVID-19 vaccines and the target should be the immunisation of high-risk groups to prevent severe disease and death. The virus will likely continue transmitting but won’t cause exactly the type of severe illness and deaths as occurred over the past year.