EU states may tighten summer travel rules amid Delta surge

"A double-dose is the best way to protect ourselves against these variants," a commission spokesperson said.

The Delta variant, first found in India, is already predominant in the UK and Portugal, but Estonia and Luxembourg continue to identify large numbers of cases related to this strain.

By the end of August, Delta is expected to make up 90-percent of infections in Europe, especially after an expected and most likely restriction-free summer, with increased travelling and domestic gatherings.

All jabs approved in the EU - BioNTech/Pfizer, Moderna, AstraZeneca, and Johnson&Johnson - appeared to be effective against the Delta variant when both doses are administrated in the case of two-shots jabs.

However, only 43 percent of the adult population in the EU is currently fully-vaccinated - with significant differences between member states.

For example, nearly 80 percent of the population in Malta is fully-vaccinated, but this is only the case for 15 percent of people in Bulgaria.

Potential fourth wave

Last year, coronavirus cases rose more gradually over the summer months, contributing to a resurgence of outbreaks and lockdowns in the autumn and winter.

According to the World Health Organization (WHO), the three conditions for a new wave of excess hospitalisations and deaths before the autumn are already in place - namely the new variants, deficits in vaccine uptake and increased social mixing.

"The vaccination coverage in Europe is not yet sufficient to protect the region from a new and dangerous resurgence of Covid-19," a WHO spokesperson told EUobserver.

As of Thursday, EU member states have registered more than 33 million coronavirus cases and over 740,800 deaths, according to statistics from the EU Centre for Disease Control (ECDC).

Cyprus, Portugal, Spain, and Ireland have all reported more than 100 cases per 100,000 inhabitants in the last two weeks - what led some EU member states to reintroduced restrictions on arrivals from these countries.

'Spaghetti of national rules'

France's European affairs minister Clement Beaune said on Thursday that he was advising French people to avoid travelling to Spain and Portugal for their summer holidays due to the risk of the Delta variant.

Germany previously imposed a 14-day quarantine requirement for arrivals coming from the UK, Portugal, India, Nepal, and Russia, but has recently eased restrictions - amid international pressure.

Concerned about the Delta variant, Lithuania has imposed a 10-day quarantine from citizens arriving from Spain and Cyprus, who are not vaccinated or do not have proof of a recent recovery.

Similarly, Slovakia has also tightened entry restrictions - obliging all non-fully-vaccinated people to undergo two weeks of self-isolation from Friday (9 July).

Although the EU Covid-19 certificate was designed to restore unrestricted travel across the EU, individual member states retain the right to impose restrictive measures, such as quarantine or testing, to protect public health.

Nevertheless, MEPs have urged member states to coordinate, arguing that citizens need clarity when travelling across the EU.

"We are again dealing with a spaghetti of national rules," Dutch liberal MEP Sophie in 't Veld said on Wednesday during the plenary.

"We are seeing the Delta variant going around so of course measures need to be taken, but they should be taken on a harmonised European basis, not a national basis," she added.