Trials begin on Covid booster jab hoped to protect against new variants

·3-min read

The first trials have begun of a Covid booster jab that it is hoped will offer good protection against a wide range of variants, researchers have revealed.

Covid jabs currently used in the UK trigger an immune response towards the coronavirus spike protein, which helps the virus get into human cells.

However, different variants of the coronavirus have different mutations in this protein, meaning a vaccine that works well against one variant may not be as effective against another.

The team behind the new booster jab hope to get around this problem by triggering an immune response towards the spike and non-spike proteins of the coronavirus.

“This vaccine targets not just the spike protein but also the nucleocapsid protein. This varies much less than the spike protein and therefore the hope is that it will be more proof against current and future variants,” said Prof Andrew Ustianowski, a consultant in infectious diseases and tropical medicine at North Manchester General hospital, and chief investigator for the study.

The phase 1 trial is a collaboration between the US pharmaceutical company Gritstone, the University of Manchester and Manchester University NHS foundation trust and is expected to involve 20 participants aged 60 and over, all of whom have previously been vaccinated with the Oxford/AstraZeneca jab. Each participant will receive the booster, with one of two different doses.

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Ustianowski told the Guardian the third and fourth participants were receiving their doses on Tuesday, with the expectation that all 20 would be dosed in the next two to three weeks. On Monday, Andrew and Helen Clarke from Bolton were the first to receive the vaccine.

Ustianowski said the trial would be looking at the safety and tolerability of the jab, as well as the boosting of existing immune responses towards the spike protein and the development of responses to the viral nucleocapsid, with results of interest expected in the next few months.

Lawrence Young, a virologist and professor of molecular oncology at the University of Warwick, who is not involved in the trial, said the new vaccine, known as a self-amplifying mRNA second-generation Sars-CoV-2 vaccine, or SAM, was really exciting.

“We need second-generation vaccines that will stimulate a broader immune response to other parts of the Sars-CoV-2 virus – not just focus on the spike protein, as do the current vaccines,” he said.

“Using parts of the virus that are less prone to change in virus variants has the potential to provoke an immune response that will be more effective against all current virus variants and any future variants that might develop. Given as a booster shot after immunisation with the current vaccines, this SAM vaccine is very likely to generate a more robust and long-lived immune response, particularly in the elderly and most at risk.”

Ustianowski said that it was difficult to predict whether the new jab would remove the need for Covid vaccines to be tweaked to tackle variants. “This is one of the hopes for this vaccine, but we will have to wait for the immunology and effectiveness data to emerge,” he said. But, he added, “it has been designed with this factor in mind”.

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