Would-be visitors to Britain this summer should expect the return of international travel to be patchy, Heathrow Airport boss John Holland-Kaye said on Wednesday.
His remarks suggest the travel industry is not confident of passengers returning in significant numbers as the UK emerges from lockdown.
Holidays abroad are currently illegal and travellers arriving from overseas are required to quarantine, although that is expected to change on May 17 with a new traffic-light system implemented. 'Green-list' passengers will not be required to quarantine on arrival.
Mr Holland-Kaye said the UK government would continue to worry about vaccination rates in other countries before travel resumes to pre-pandemic levels.
"The nature of international travel is that you’ve got to think of both ends of the route," he told an aviation forum.
"Unless the UK government is confident about vaccination levels, or the risk of importing Covid-19 from overseas, then they’re not going to open their borders with other countries. That’s why over the summer we’re going to see a patchy opening up of international travel, which I hope will progressively improve."
EU countries agreed on Wednesday to launch Covid-19 travel passes as a step towards re-establishing summer tourism.
Certificates would allow those who are vaccinated, who have recovered from Covid-19 or who produced a negative test result more freedom to travel within the EU.
John Holland-Kaye urges against excessive caution
Mr Holland-Kaye said the government should not be too cautious as the pandemic situation improves. Before it takes effect, the proposal must be endorsed by the European Parliament, which is due to discuss the matter this month.
"We know that international travel is a vector for carrying this virus around the world so we do need to be responsible, but until we get people flying again we won’t have a business," he said.
"There’s a difficult balance we all have to make in our work with government to make sure we’re not pushing people to go too far and too fast.
“But equally, we’re not encouraging them to be too cautious because the government has to balance the economic needs with the health issues, and we’re coming close to a tipping point for that."
Pressure was also mounting on the government to ease restrictions faster as official figures showed nearly a quarter of registered Covid-19 deaths in the UK were not caused by the disease.
Latest Office for National Statistics data showed that 23 per cent of coronavirus deaths registered in the UK were among those who died with the virus rather than from the illness, meaning Covid-19 was not the primary cause of death.
Separate records show that the daily coronavirus death toll has not exceeded 28 deaths a day since the start of the month, despite government figures charted below being higher.
This is because the daily update could be affected by delayed reporting from local health authorities.
A study by the University of Oxford suggests the number of people in hospital with coronavirus could be about half the daily published figure.
About 1,570 people were admitted to hospital with Covid-19 in the past seven days, a 19.7 per cent decrease on the week before, the government's coronavirus dashboard figures showed. There were 23 deaths on Tuesday and 2,472 new cases.
The positive data came as scientists said the UK could be only months away from offering people “mix and match” Covid-19 vaccines, which could speed up the immunisation campaign because patients would no longer need to be offered only one type of vaccine.
The time between first and second doses would then be reduced because overall supply would be higher.
A University of Oxford trial is looking at whether combining vaccines might give people broader, longer-lasting immunity.
Adults over 50 who have had a first dose of the Pfizer-BioNTech or AstraZeneca-Oxford drugs were encouraged to take part in the trial.
Their second dose could be the same again, or a shot of Moderna or Novavax.
Prof Matthew Snape from the Oxford Vaccine Group said combining vaccines could speed up inoculation campaigns around the world.
He said the UK's vaccine drive could be adapted "within the next few months" if the study was successful.
"If we have flexibility in which vaccines we give for the second dose or later doses it massively increases the flexibility and resilience of the immunisation programme and would mean we could roll these vaccines out more quickly – not just in the UK, but internationally," he told the Today programme on BBC Radio 4 on Wednesday.
“There are some studies that suggest a combination might give a better immune response overall, which would be better still.”
Meanwhile, scientists highlighted the threat of the variant first identified in South Africa, which has been detected in large numbers in south London this week.
Authorities started the UK's biggest surge testing campaign to date in response to the infections.
Prof Peter Openshaw from Imperial College London said the variant could reverse the positive progress made in recent months.
"A lot of scientists are very concerned about what's happening at the moment,” he said.
"I think we're all just hoping that the staged reduction in lockdown is going to be OK. It is being done reasonably cautiously, but this is not good news.
"If we get rapid spread of the South African or other more resistant variants, it may well be that we are going to have to put the reductions of lockdown into reverse."
Some MPs were pressuring Prime Minister Boris Johnson to ease lockdown measures across the UK more quickly in light of the positive data.
However, on Tuesday he urged caution on the lifting of restrictions and said it was the lockdown and not vaccines that had kept Covid numbers low.
“It is very, very important for everybody to understand that the reduction in these numbers – in hospital admissions, in deaths and infections – has not been achieved by the vaccination programme,” he said.
“People don’t, I think, appreciate that it’s the lockdown that has been overwhelmingly important in delivering this improvement in the pandemic and in the figures that we’re seeing.”
More on coronavirus
Europe scrambles to revive vaccine plan after Johnson & Johnson halts exports
