Antibodies

Do Americans need a third booster shot of the Pfizer vaccine? The question is the subject of a remarkable row between the drugs company and the government — the former of which is putting together an application for emergency use authorization for a third dose and the latter of which has so far proved unwilling to sanction it. The Department of Health and Human Services issued a statement after a meeting on Monday saying: ‘At this time fully-vaccinated Americans do not need a booster shot.’ For its own part, Pfizer cites evidence from Israel which, thanks to a deal with Pfizer, was able to get ahead in its vaccination program in return for the country effectively being used as a giant human laboratory.

The UK policy of delaying second doses of the Pfizer vaccine has been criticised by some as risky, with Pfizer warning that there is no data on the effectiveness of its vaccine other than for the dosing regime used in phase 3 trials: two doses, 21 days apart. But evidence is steadily trickling through. Earlier in the week I wrote here about the Scottish population-wide study which found that a single dose of the Pfizer vaccine reduced hospital admissions by 85 per cent between 28 and 34 days after the jab. This morning comes Imperial College’s React-2 study, which paints a picture that is, on the face of it, rather less flattering. It tested 154,000 people for the presence of antibodies to SARS-CoV-2, the virus which causes Covid-19.

Just how strong an immunity do Covid patients develop after they have acquired the infection and how long does it last? The question is vital to the likely future passage of the pandemic, and to how well vaccines will protect us in the long term. Several studies have suggested there is a sharp decline in antibodies to SARS-CoV-2 over time – a paper from Imperial College’s React study in October, for example, revealed that the proportion of the population showing antibodies to the virus declined from 6 per cent in June to 4.4 per cent in September. The researchers were at pains to emphasise that the presence of antibodies does not indicate immunity to Covid-19, but many people have taken it as an indication that immunity to the disease quickly declines after infection.

The Israeli government is reporting this morning that the country’s Institute for Biological Research has made a breakthrough in the development of a potential treatment against SARS-CoV-2, the virus which causes Covid-19. Scientists there have isolated a ‘monoclonal neutralising antibody’ which could potentially neutralise the virus after infection. The antibody was obtained from the blood of an infected patient. It is called monoclonal because it is generated from a single cell – which could allow vast quantities of the antibody to be produced quickly. Is it the breakthrough that could make all the difference? Treatment of novel viruses with monoclonal neutralising antibodies has been under development for some time, notably for Ebola, SARS and MERS.