The announcement made by the government yesterday makes it easier for people vaccinated in Europe or the USA to travel to England.
Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:
“Vaccine roll out in the UK has had a massive impact by breaking the link between infection and serious disease. The evidence also indicates that they are significantly reducing infection and onward transmission. Therefore, it makes sense to acknowledge the reduced risk posed by fully immunised people. However, we shouldn’t be gung ho with relaxations. We have a wealth of data on performance of the vaccines used in the UK, but not all vaccines are the same, and we should take into account the relative effectiveness of other vaccines when formulating a policy that continues to protect the UK.”
Dr Peter English, Retired Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice, Immediate past Chair of the BMA Public Health Medicine Committee, said:
“Our aim, in this pandemic, has to be to do all that we can to prevent people from getting ill (including long term consequences of Covid-19), dying, and putting a strain on the NHS by requiring hospital admissions and/or critical care; while at the same time minimising the harms caused by restrictions.
“Clearly, there is a balance to be struck here; and few if any public health or health and safety interventions can be expected to reduce one risk to zero without increasing a different sort of risk.
“We therefore need, wherever possible, to employ restrictions that are minimally harmful and maximally effective (like wearing masks in enclosed spaces).
“Restrictions on travel, including quarantining, are likely to have a very considerable effect on people’s ability to travel, so we need to be sure we only require such restrictions when they are most effective.
“So – how does vaccination fit in?
“When a new vaccine is introduced, its efficacy in trials and its effectiveness in the real world, in terms of preventing infection, and different levels of illness in recipients, can be estimated reasonably quickly. A vaccine’s effectiveness at preventing onward transmission – secondary prevention – is much harder to measure with any degree of precision, although we do know none of the people in whom the vaccine preventions infection will transmit the disease, and we also know it is by no means 100% effective – we know that some people have been infected and gone on to infect others, despite having been fully vaccinated. We have good evidence on vaccines’ effectiveness at preventing infection. The latest PHE report1 states: “With the Pfizer-BioNTech, estimates of effectiveness against infection range from around 55 to 70%, with the Oxford-AstraZeneca vaccine they range from around 60 to 70% (5, 12, 13, 14). With 2 of 2 doses of either vaccine effectiveness against infection is estimated at around 65 to 90% (5,12).”
“Since people who have been fully vaccinated are 65-90% less likely to be infected, the odds that any traveller who has been fully vaccinated must be only 10-35% of the odds that an unvaccinated traveller will be infected.
“It is taking much longer to accumulate evidence on how effective vaccination is at preventing people from infecting others, given that some people will be infected, but will likely, nevertheless, be less likely to infect others. Some evidence is accumulating (e.g.,2-7). There is growing evidence of the overall level of effectiveness against onward transmission, over and above the likelihood of being infected (although I would hesitate to try to quantify this at present).
“The judgement by politicians (well informed, one must hope, by expert advice from SAGE) must be that the likelihood that fully vaccinated individuals will be infected on entry to the UK, and able to infect others if they are, is insufficient to justify the costs of quarantine.
“This does not mean that they believe there is no risk of importing cases, just that the risk is considered too low to justify the harms of quarantine.”
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Prof Jonathan Ball: “Receives funding to develop next generation Covid19 vaccines.”
Dr Peter English: “Dr English is on the editorial board of Vaccines Today: an unpaid, voluntary, position. While he is also a member of the BMA’s Public Health Medicine Committee, this comment is made in a personal capacity.”