Week 7: Vaccines

As an immunologist, during the pandemic, I was often asked for my opinion on when vaccines might be developed, how effective they would be, whether immunity would last, and whether new viral variants would evade the immunity produced by vaccines or natural infection. For this introduction, I just wanted to give you my own personal perspective on how these areas developed between 2020 and 2023.

When the SARS-CoV2 virus was first identified, there was much discussion about how long it would take to develop a vaccine or whether it would even be possible at all. Even in February 2020, I thought that a vaccine could well be produced in a laboratory within a few months, and an effective vaccine could be available within the year. The technology for vaccine development had come a long way in the last 20 years, and I had a reasonable expectation that it could be applied quickly to the novel virus. I was much less certain about how long it would take to complete vaccine trials. However, as it happened the urgency of the pandemic meant that trials were accelerated so as to quickly identify effective vaccines.

While I thought that effective vaccines would be developed quickly, what surprised me is that the vector vaccines such as the one produced by Oxford/AstraZeneca and the mRNA vaccines were the ones to emerge first from the development and testing process. By comparison vaccines produced by more traditional methods – that is from virus components or using inactivated virus – took longer to develop than those developed by the new methodologies. Even more surprising was just how effective these new vaccines were in practise.

Another big question was how long immunity might last, particularly when new viral variants were arising. It became progressively clearer that none of the viral variants up to 2023 could completely evade protection produced by vaccination or infection with earlier strains. Although reinfection with new strains happened regularly, some protection remained and the numbers of cases of severe disease was lower in later waves of infection, caused by new variants.

Right from the start of 2020, I thought that the virus would produce a number of waves of epidemic infection, but eventually become endemic after 2-4 years, as many other respiratory viruses, including coronaviruses, have done over the centuries. It looks like this has turned out to be true. We may get new variants of SARS-CoV2, and some years the level of infection and disease may be worse than others, but we will not go back to the situation we had in 2020, when there was essentially a novel virus and no population immunity at all to the virus.

What we have learnt from the COVID-19 pandemic should give us important insights and a head-start into how we handle any future novel pandemic viruses.