A disturbing trend has emerged in the world's most vaccinated country as the Delta variant continues to spread.
In Israel, 5.2 million of its 9.3 million population have been fully vaccinated, however the Pfizer injection's effectiveness has dropped to 64 per cent compared to 95.8 per cent in February.
"This decline has been observed simultaneously with the spread of the Delta variant in Israel," the Ministry of Health wrote on its website.
It added the vaccine however had still averted 93 per cent of severe illnesses and hospitalisations, compared to about 99 per cent in February.
The number of registered infections has been rising significantly for about two weeks in Israel, fuelled by the more virulent Delta strain first detected in India.
On Sunday, 334 people tested positive, according to the health ministry.
The last time more than 300 new cases were recorded in one day was in early April.
Many of those infected were younger people.
The number of people severely ill with COVID-19 increased slightly to 35. No deaths related to the virus have been recorded for about two weeks.
Israel a warning to other countries
Israel has been considered a model country in the battle against the coronavirus because of its rapid vaccination campaign.
Its current infection trends could point to struggles other countries will face, even if they have inoculated much of their populations.
Israel has about 56 per cent of the population vaccinated so far and has largely used only the Pfizer-BioNTech jab.
The decline in vaccine effectiveness also coincided with the end of social distancing restrictions in Israel.
The vaccination campaign saw daily cases drop from more than 10,000 in January to single digits last month, spurring Israel to hakt nearly all social distancing requirements.
A Pfizer spokesperson declined to comment on the data from Israel, but cited other research showing that antibodies elicited by the vaccine were still able to neutralise all tested variants, including Delta, albeit at reduced strength.
Data scientist Eran Segal of Israel's Weizmann Institute of Science said the country was unlikely to experience the high levels of hospitalisations seen earlier in the year since there were much fewer critically ill.
He said it was fine to "continue with life back to normal and without restrictions" while stepping up measures like vaccination outreach and ensuring testing for Israelis returning home from abroad.
With AAP and Reuters
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