Do I need a Covid booster jab to travel abroad this winter?

Several countries have set expiry dates for fully vaccinated people, as we learn more about waning immunity

A health worker checks the body temperature of passengers bound for Frankfurt at Dubai International Airport.

Emirates Boeing 777 aircraft are seen on the tarmac at Dubai International Airport.

Passengers bound for Frankfurt board a shuttle bus at Dubai International Airport.

A flydubai aircraft is parked on the tarmac of Dubai International Airport.

Passengers check in at Dubai International Airport.

An information board displays an alert for passengers to maintain distance from others at Dubai International Airport.

Mask-clad passengers bound for Frankfurt walk past check-in counters at Dubai International Airport.

A mask-clad employee walks in front of a flydubai aircraft on the tarmac of Dubai International Airport.

Passengers bound for Frankfurt wait at a terminal of Dubai International Airport.

Passengers bound for Frankfurt wait at a terminal of Dubai International Airport.

Passengers bound for Frankfurt wait at a terminal of Dubai International Airport.

Passengers wait at a terminal at Dubai International Airport, as Emirates resumed a limited number of outbound passenger flights.

An Emirates aircraft takes off from Dubai International Airport.

Emirates Airbus A380 and Boeing 777 aircraft are seen on the tarmac at Dubai International Airport as the airline resumed a limited number of outbound passenger flights.

Passengers are assisted at the check-in counter in a terminal at Dubai International Airport.

Passengers have their travel documents checked before departure at Dubai International Airport.

Passengers have their travel documents checked before departure at Dubai International Airport.

The vast majority of people in UAE - more than 86 per cent - are fully vaccinated.

And many of those who received their last Sinopharm shot more than six months ago have already received a single booster.

But is that enough to travel abroad this winter?

Many countries only recognise one of the big four - Oxford-AstraZeneca, Pfizer-BioNTech, Moderna and Johnson & Johnson - but not Sinopharm and Sputnik.

And some countries have now set expiry dates for the duration people have been vaccinated for to ensure passengers are protected against the disease.

Here, we take a look at what you need to know before flying this winter.

Travellers from the UAE

The UAE government encourages people who had a Sinopharm vaccine more than six months ago to get a booster, which could either be Sinopharm or Pfizer, to maintain protection against the disease.

Authorities also allow people to take a full course of Pfizer, two shots, after receiving Sinopharm more than six months ago, allowing them to travel to places that do not recognise Sinopharm.

Which countries require booster shots?

It all depends on the country in question you are visiting, so be sure to check.

Some countries have set expiry dates on vaccine validity.

In the summer, Croatia became the first country to do this when it said people should be fully vaccinated within 270 days, which is around nine months, of arrival. The period has since been extended to a year.

People with vaccines administered earlier than this must take a PCR test on arrival in Croatia and self-isolate until they receive a negative result. If they cannot get tested, they must isolate for 10 days. Sinopharm is recognised by Croatia.

In Austria, you are considered vaccinated for one year, beginning on the 22nd day since your first shot. Anyone who was vaccinated before that period must show proof of a recent Covid-19 test and self-isolate for up to 10 days. Sinopharm is recognised by Austria.

Israel has added an expiry date of six months to all vaccine passports, known as the Green Pass, required to enter indoor venues.

And Vietnam requires travellers to have received a vaccine dose within a year to visit Phu Quoc, an island off the coast of Cambodia in the Gulf of Thailand, once it reopens for tourism in November. If you have not received a booster shot, you will not be permitted entry.

Which countries have set expiry dates for fully vaccinated status?

Most countries do not require boosters but many do ask travellers to be vaccinated against the virus to enter.

Some recognise only certain vaccine certificates, depending on where they were issued, so it is best to check this before booking travel.

In the UK, there is no requirement for a booster but people should have completed the full course of one of the four vaccines recognised in the country, which are Oxford-AstraZeneca, Pfizer-BioNTech, Moderna and Johnson & Johnson.

If you were inoculated with a two-dose vaccine, which is all of the above but Janssen of Johnson & Johnson, you must have had both doses to be considered fully vaccinated. The second dose must have been administered more than 14 days ago. Sinopharm is not recognised by the UK but vaccine certificates for shots recognised in the UK are accepted from the UAE.

In Switzerland, it has been mandatory to provide proof of inoculation in the form of a Covid-19 vaccination passport since September 13 to enter many public places, such as restaurants, cafeterias and more.

However, if the traveller was vaccinated in a country outside the European Union and the European Economic Area, their certificates will not be accepted. Anyone in this position travelling to Switzerland will have to test for Covid-19 every three days.

A woman receives her third dose of the Covid-19 vaccine in Israel. Boosters induce stronger immune responses, studies show. Reuters

Why are boosters required?

To maintain protection against the virus. Neutralising antibodies have been shown to fall fairly fast after either vaccination or infection with the coronavirus.

A recent study in the UK found an increased number of breakthrough infections among those who were vaccinated three months previously.

Experts on the Imperial College London-led React-1 study monitored home swab tests taken by more than 100,000 people in England between September 9 and 27 and 764 were positive for the virus.

Among those fully vaccinated, the prevalence of infection (0.55 per cent) was higher for those who had their second dose of vaccine three to six months ago, compared with those who had received their second shot less than three months ago (0.35 per cent).

Is the immune response stronger after a booster than the primary series?

Yes, a booster should induce stronger immune responses.

“It will boost,” Rafi Ahmed, an immunologist at Emory University in Atlanta, told science journal Nature.

After vaccination, the body creates a surge of different types of antibodies to fight the illness, as it would in response to a real infection. They slowly drop but some improve in quality over time.

A booster causes a surge in neutralising antibodies and memory B cells, which circulate in the bloodstream, sometimes for decades, until the body encounters the pathogen again.

B cells produce antibodies and are the main players in the protective immune response against infections.

They will fade again but the number left over will be bigger than before, which will create a faster and more forceful response. The quality of the B cells triggered by the vaccine also mature, which helps them bind to the virus more efficiently.

Experts say the number of antibodies and memory B cells will eventually plateau, either due to repeated boosting or infection.

But it is unlikely such levels have been reached in those who have had the recommended regimen of Covid-19 vaccine or a previous infection, Ali Ellebedy, a B-cell immunologist at Washington University in St. Louis, Missouri, told Nature.

Green pass status on the Al Hosn app - in pictures

A security guard wearing gloves checks the vaccine status of a guest at a bar in the Radisson Blu hotel in Dubai Media City. Pawan Singh / The National

Patrons wait to have their Al Hosn vaccine app checked at the Radisson Blu in Dubai Media City. Pawan Singh / The National

Licensed premises with a bar licence, rather than a restaurant licence, are required to check that all guests have had a vaccine or a recent PCR test. Pawan Singh / The National

The latest requirement cuts the risk of people spreading the virus. Pawan Singh / The National

Staff check the Al Hosn app before guests can enter bars and restaurants on Friday, June 11. Pawan Singh / The National. Story by Patrick