The highly infectious (but potentially less severe) Delta strain of Covid-19 has rendered the concept of herd immunity “mythical,” Professor Andrew Pollard, director of the Oxford Vaccine Group – the research entity which partnered with AstraZeneca to produce its coronavirus vaccine – has said.
“The problem with this virus is [it is] not measles. If 95 percent of people were vaccinated against measles, the virus cannot transmit in the population,” Pollard said, speaking to UK lawmakers from the parliamentary group on Covid-19 on Tuesday.
“The Delta variant will still infect people who have been vaccinated. And that does mean that anyone who’s still unvaccinated at some point will meet the virus…and we don’t have anything that will [completely] stop that transmission,” the academic warned.
At the same time, Pollard dismissed the need for booster vaccinations, saying boosters would be needed in a situation of an increase in hospitalisations or deaths among the vaccinated. “And that is not something we are seeing at the moment,” he said.
Pollard further added that even as vaccine-induced heightened antibody levels drop, vaccinated people’s immune systems are likely to remember the vaccinations for “decades,” thereby offering a level of protection in case of renewed exposure to the virus. “So, there isn’t any reason at this moment to panic. We’re not seeing a problem with breakthrough severe disease,” the professor assured.
Natural infections are also known to provide such "cell-memory-based" protection.
The immunologist suggested the virus is likely to continue to mutate, coming up with “a variant which is perhaps even better at transmitting in vaccinated populations. And so that’s an even more of a reason not to be making a vaccine programme around herd immunity,” he stressed.
Pollard went on to say that there was nothing the UK could do to stop new variants from emerging, and that the country should focus instead on preventing hospitalisations and deaths, not just in Britain but around the world.
The academic’s comments come on the heels of the publication of a study earlier this month by Imperial College London’s national coronavirus study programme, REACT-1. The study, which was based on a sample of over 98,000 Britons in England, concluded that the Delta variant has dropped vaccine effectiveness in stopping infections to 49 percent between late June and early July, with protection against symptoms also declining, from 83 percent to 59 percent, during the same period. These figures prompted REACT-1 to suggest that the creation of a new vaccine meant specifically to target Delta may be in order.
The Oxford-AstraZeneca Covid vaccine created with the help of Pollard’s researchers is one of three preparations approved by Britain’s National Health Service, alongside Moderna and Pfizer/BioNTech. A fourth vaccine, developed by Johnson & Johnson subsidiary Janseen Pharmaceutical, is expected to be made available later this year.
The UK has one of the highest coronavirus vaccination rates in the world, with nearly 90 percent of adult Britons receiving at least one dose to date. Despite the vaccination drive, the country recently faced a spike in infections between May and July that outpaced infection levels for most of 2020 and came close to matching the December 2020 highs. Fatalities remain far below last year’s peak, however, with health officials attributing this to vaccinations. The UK reported 23,297 cases and 146 deaths on 10 August.
In spite of Pollard’s recommendations, UK Health Minister Sajid Javid announced plans Tuesday to begin a Covid booster programme in early September. Before that, the government announced that teenagers as young as 16 years old would be allowed to vaccinate, but stressed that vaccinations would not be mandatory. In July, authorities ruled against vaccinating most children.
While medical professionals are united in the opinion that the Delta strain of Covid is more transmissible than the virus’ original variant, they are divided regarding its severity compared to other variants of the virus. According to the American Society for Microbiology, Delta, which is responsible for the majority of new cases in many countries, is about 40-60 percent more transmissible than the Alpha strain, and nearly twice as transmissible as the original Wuhan strain, but that its symptoms are generally mild, and limited to fever, headache, sore throat and runny nose, but no cough or loss of smell.
However, other studies, based on reports coming out of India, where Delta originated late last year, point to more severe symptoms, including stomach pain, nausea, vomiting, loss of appetite, joint pain and even hearing loss.