10th April 2020 – Our Own Immune System is the Key to Success


A Blog by Dr David J Flavell PhD FRCPath
Charity & Scientific Director of Leukaemia Busters

10th April 2020

Immunity & Vaccination

In todays blog:

  • Immunity to COVID-19 is likely!

  • Massive international research effort

  • Vaccination is long term key to the problem

  • The need to plan properly for future pandemics

Let me start my blog today with some reassuring words and spell out how I believe we will beat the COVID-19 problem in the near future. Never before in the history of global biomedical sciences have so many academic and commercial organisations come together to solve a single common problem and never before have we had such advanced technology to assist us in the task.

It is not only the COVID-19 pandemic that is unprecedented in modern times but also the outstanding global response there has been to it and it is that which will assure our victory over this and other similar infectious pathogens we will face in future. The awful experience that the entire world is going through right now is a wake-up call and will I believe transform the way scientists and government agencies deal with these types of problem in future.

Everyone is on a steep learning curve so let’s hope everyone remembers this and that the WHO acts out its role to the full in devising a universal response that all nations must follow when this happens again at some indeterminate point in the future. It’s the extent and speed of the current global response that gives me the confidence to predict that the answers to defeat COVID-19 will arrive far more quickly than they would have in normal times as we adapt and adjust to the urgency of the situation.

With those words of encouragement let me now focus today on two key aspects of the solution; firstly acquired immunity to the coronavirus that causes COVID-19 and secondly the R & D work that is currently underway to develop an effective vaccine against the coronavirus and the likely time it will take before an effective one becomes available for use in the general global population.


Firstly be reassured that patients who have recovered from COVID-19 must have developed immunity to the virus because if they hadn’t they would never have recovered from the infection in the first place.

That said the evidence for long lasting immunity in COVID-19 is currently non-existent simply because the virus is so new it’s not possible to assess how long immunity might persist for. So called “acquired immunity” is the result of our formidable immune system that leaps into action when it encounters things recognised as non-self, resulting in the generation of antibodies that neutralise the virus together killer white blood cells that destroy any cells still infected with virus.

Sometimes such acquired immunity lasts a lifetime as with the polio virus but then with others it may only be relatively short lived, perhaps a few months or years. The thing is because the COVID-19 coronavirus is so new on the scene, currently just over three months since the first cases, nobody knows yet how long immunity persists for or indeed even if everyone that has had the virus is fully immune to re-infection.

There have been some alarmist anecdotal stories that some individuals in China, Japan and South Korea appear to have been re-infected with the same coronavirus. These reports should be treated with caution as on closer examination these were all patients who having had the virus appeared to recover and then were discharged from hospital only to fall ill and test positive once again.

It is more likely that in these cases they never really recovered fully from their first infection and continued to harbour the virus until it reappeared once again later, so not really a reinfection but a relapse of their original illness.

You can take comfort in the fact that with the original SARS coronavirus epidemic of 2002/03 and the similar coronavirus that caused the Middle East Respiratory Syndrome (MERS) outbreak in 2009, patients did produce virus neutralising antibodies that were protective for between one to two years after infection.

Add to that the fact that a small experimental study in rhesus macaque monkeys that had been previously infected with the SARS-CoV-2 virus that causes COVID-19 could not be re-infected when challenged with the same virus weeks later. So the evidence, though tentative at this stage, is building to support the notion that there is a build-up of acquired immunity in COVID-19 patients that should protect them from further re-infection.

That of course is the great hope but has yet to be fully proven through additional studies that will extend for years into the future where antibody levels continue to be monitored in past COVID-19 patients. Take heart though, my instinctive feeling as an immunologist is that immunity is much more likely than not so relax and sleep easy at night, as I do.


Moving on now to vaccines for COVID-19. In my blog on the 7th April “Vaccinating the Herd” I described the various types of vaccines that can be used to develop a vaccine for COVID-19 and explained some of the roadblocks to developing one that is successful. I also explained that an effective and safe vaccine is probably the only long term solution that will ultimately get the world out of the current situation permanently, for this particular virus at least.

Since I wrote that blog just a few days ago the pace and speed of vaccine development by commercial and non-commercial research organisations has picked up significantly and there are now 78 candidate vaccines in active development and possibly a further 37 candidates waiting in the sidelines.

The global response to vaccine development has been unprecedented and is a reflection on how seriously the global biomedical community views this pandemic and the necessity to get the world back on to a normal footing as quickly as possible.

The first vaccine has already entered early phase clinical trial in normal participants in Seattle with a messenger RNA (mRNA) vaccine from Moderna, a Cambridge, Massachusetts based pharma and was super-fast tracked from inception to the first human participant dosing in just 61 days, a breathtaking record time.

To put this into perspective the normal timeline for vaccine development is normally somewhere between five to ten years. The crisis has seen a tectonic shift in the usual paradigm of vaccine development but others are concerned that super-fast tracking means that there has been inadequate testing prior to human vaccination may that might compromise safety and efficacy of the vaccine in human subjects.

Still it is argued, these are desperate times that need desperate measures and the usual safety and efficacy values may need to be relaxed to meet the crisis head on. The trouble with this is that we may end up with some vaccines that damage the recipient and others that don’t work.

My view is that there is a consensus view growing that the old rule book for vaccine development (and by inference other experimental drugs for COVID-19) will need rethinking to meet the crisis, something that could shift the paradigm.

To read our other blogs click here.