Covid-19 reader: 27 August

Are vaccines offering less protection?

Danny Altmann, professor of immunology at Imperial College London, BBC Radio 4’s PM broadcast

There are growing concerns about fading vaccine efficacy, particularly in the face of the Delta virus, which is now the dominant strain across the world. However, there are different claims being made, based on different studies – all of which contributes to an often confusing picture. Danny Altmann, professor of immunology at Imperial College London, was interviewed on Radio 4’s PM news programme to try to make sense of it all.

‘I’ve previously waxed lyrical about how amazing the vaccines are and what great protection they give us and how it is hard even for the variants to beat that – and I still stand by that as far as I can,’ he said.

However, he said that the Delta variant was really stress testing the vaccines and assumptions. ‘We can all see examples of healthy people, who seem to be in their prime and have evidence that they have made really good immune responses to the vaccine, but have been infected by Delta and got not just ill but quite reasonably ill – a week or two in bed feeling really rough,’ he said. ‘So the vaccinations are still holding up. But like all other countries, we are seeing this massive number of breakthrough infections that aren’t quite filtering through into hospitalisations and deaths, but aren’t trivial.

Does this make a case for an autumn booster campaign, following the likes of Israel and the US, which have already taken the decision to boost? Professor Altmann said this was ‘tricky’ and there was not yet enough information in the UK to support boosting across the board. ‘We’ve simply not got the data on whether the majority of us, with quite a lot of immunity on board, would really get any more out of a third boost,’ he said.

Professor Altmann was asked why the UK has the highest number of cases in proportion to its population, when most countries are now in a similar position in terms of combatting the Delta variant and have similar vaccination levels. However, he offered no simple explanation. ‘As we get 18 to 19 months into the pandemic, it becomes ever more complex and ever more nuanced,’ he said. ‘And there are very fine margins where the virus punishes us for very small marginal differences in policy and practice and health and healthcare.’

Evidence of continued vaccine efficacy

Centers for Disease Control and Prevention (US), report

A quarter of just over 43,000 Covid-19 infections in the US county of Los Angeles in July were in fully vaccinated people, according to a study published in the US Centers for Disease Control and Prevention’s Morbidity and mortality weekly report. A further 3% were partially vaccinated and the rest (just over 71%) were unvaccinated. On 25 July infection and hospitalisation rates among unvaccinated people were 4.9 and 29.2 times those in fully vaccinated people. While the vaccines used (Pfizer/BioNTech, Moderna or Janssen) clearly don’t offer full protection against infection – and have never been claimed to do so – the study was said to show that they did protect against infection and severe Covid-19, even with increased community transmission of the predominant Delta variant. The research points out that the findings are similar to those from other recent studies indicating that Covid-19 vaccination protects against severe infection in areas with increasing prevalence of the Delta variant. And it calls for further efforts to enhance Covid-19 vaccine coverage.

Infection risk much greater than vaccine complications

University of Oxford study, BMJ research paper

There are increased risks of developing dangerous blood clots after Covid-19 vaccination, but these are far lower than the risks of the same problems following coronavirus infection, a new study has found.

The research, by a team at the University of Oxford, covered a population of 29 million vaccinated people in England. It looked at the incidence of blood clots and thrombocytopenia (a condition associated with low platelet counts), as well as cerebral venous sinus thrombosis (CVST) and ischaemic stroke.

The study did find increased incidence of thrombocytopenia and other rare blood clots after a first dose of the Oxford/AstraZeneca vaccine. And there was a higher risk of blood clots in arteries and ischaemic stroke with the Pfizer/BioNTech vaccine. However, the risks of such problems were much greater following a Covid-19 infection.

Specifically, the research paper published in the BMJ said there were 107 excess events (hospitalisation or deaths) of thrombocytopenia per 10 million population related to the AstraZeneca vaccine. But this compared to an estimated 934 extra cases following a Covid infection. A further 66 excess events of venous thromboembolism (blood clots in the veins) represented a risk that was several hundred times lower than that following an infection. And the 143 extra cases of ischaemic stroke per 10 million associated with the Pfizer/BioNTech vaccine was 12 times lower the 1,699 following infection.

The paper concludes that ‘the risks of these outcomes after vaccination were much lower than those associated with Covid-19 infection in the same population’. ‘These are really reassuring results to underscore the safety of the vaccine,’ lead author of the research, Julia Hippisley-Cox, professor of clinical epidemiology and general practice at the University of Oxford, told the BBC.