Simulating the Covid-19 vaccine rollout

T

he Pitch study, conducted at Oxford University, recently found that an interval of eight to ten weeks between doses of the mRNA Covid-19 vaccine developed by Pfizer appears to boost the effectiveness of immunisation compared to a shorter spacing.

The UK Government drew a lot of criticism following its decision to administer vaccine doses 12 weeks apart at the beginning of its rollout but stretching out the interval from the three or four-week wait faced by study participants appears to have paid off.

Nevertheless, incoming data and the threat of the Delta variant prompted a recent decision to cut the time between jabs to eight weeks.

UK Vaccines Minister Nadhim Zahawi said: “As we raced to offer a vaccine to all adults, we took the JCVI’s [Joint Committee on Vaccination and Immunisation] advice to shorten the dosing interval from 12 to eight weeks, to help protect more people against the Delta variant.

“This latest study provides further evidence that this interval results in a strong immune response and supports our decision.”

Around the same time the Oxford researchers published their findings, biosimulation company Certara announced that its Certara Vaccine Simulator tool had predicted these same results six months previously.

The Certara Vaccine Simulator, which is based on the company’s quantitative systems pharmacology (QSP) technology, uses factors such as bioinformatics and in-vitro assays to develop medical modelling tools. These tools can then be used to answer different questions about vaccines that may not yet be answerable in real-life clinical studies, such as the best dosing strategies for different patient cohorts.

The simulator has even been used as part of a US Food and Drug Administration (FDA) submission by Japanese pharmaceutical company Daiichi Sankyo, which used the tool to estimate the ideal dosing interval of its mRNA vaccine.

To find out more, we spoke to Certara QSP senior vice-president Piet van der Graaf about the future potential of the technology.

At Certara we have been developing patient platforms for years, which we can then use to simulate clinical trials before we actually run them. We have been working on a specific platform for nearly five years, in a consortium with major pharma companies, that we call the immunogenicity simulator.

The purpose of that platform is to predict undesired immune responses when you give a biological therapeutic to patients, which is a significant issue in their development. We’ve been working on this platform for several years and when the Covid-19 pandemic hit last year we started to think about what we could do to make a contribution.

We realised that our immunogenicity platform was exactly that – it already had all the components of the human immune system inside it. All we had to do is flip its purpose on its head. The purpose for the biological therapeutic is to minimise the immune response, whereas with vaccines you try to do the opposite and create a strong immune response.

We ran a small pilot in the summer of last year where we put the spike protein sequence into our simulator to see what happened and it seemed to predict a meaningful antibody response.

We began working with Daiichi Sankyo and helped them design a clinical trial for a novel mRNA Covid-19 vaccine that hadn’t been tested in humans using our platform, and these results were submitted to regulators in support of a Phase I trial in December of last year.

Pfizer and Moderna had been using a three- or four-week dosing interval for their mRNA vaccines. Our modelling suggested that wasn’t optimal and the time between the first and second booster should be increased.

Very interestingly, a study came out recently that shows that the optimal time between dose one and two is eight weeks, exactly as we predicted half a year ago.

With our model, we can simulate any scenario. Our simulation showed that the efficacy increases up to an interval of eight weeks, and then it starts to plateau and tail off.

We also concluded that the 12 weeks the UK Government decided on a long time ago, which was mainly driven by lack of supply, was probably at the long end of the optimal dose.

We can now also answer questions about the annual booster dose. We need to wait for another half year or so before that becomes relevant, but we have already run virtual trials over two or three years which can show whether and when you might need a booster dose.

Another example of the kinds of virtual trials we can do is looking into whether you can combine vaccines. Can you just give people whichever vaccine is available for their first and second dose, regardless of manufacturer? Would that be a good or bad idea, or would it make no difference at all?

We also happen to have a similar virtual patient simulation platform for oncology. We’ve been building that for several years with major pharma companies and the main focus has been on combination therapy, how to combine different immuno-oncology targets in the best possible manner and which patients benefit most. We’ve also been investing heavily in neuroscience, specifically Alzheimer’s.