The data show that 1,19,401 positive cases were reported from Kerala in the past 15 days, from October 19 to November 2. Of these, the data show, 1,00,593 had been eligible for vaccination of which 67,980 (57.9 per cent of the total case count) had got either both doses or a single dose.

Of those eligible for vaccination among the positive cases, 40,584 (34.9 per cent of the total count) were fully vaccinated and 27,396 others (22.9 per cent of the total count) had only one dose — the rest had no vaccine history.

Kerala Health Minister Veena George said the trend of breakthrough infections was anticipated — and pointed out that it also proved that vaccination could prevent the severity of infection.

The Minister said in the last one week, only around 2 per cent of the 77,516 active cases required oxygen beds and about 1.5 per cent needed ICU admission.

The state has so far ensured the first jab for 95 per cent of the eligible population, whereas 52 per cent of them got both doses.

At present, around 50 per cent of the daily case count in India is being reported from Kerala, which also accounts for 45 per cent of the active cases in the country.

“Kerala has got immunity mainly from vaccination rather than infection as revealed by the state’s recent seroprevalence survey. In many other states, high prevalence of antibodies was mainly due to the widespread infection,’’ George said.

“Although fully vaccinated persons are getting infected, deaths among them due to Covid are very rare. In cases where fully vaccinated people died, the victims had been either very old or had severe comorbidity factors,” she said.

Officials said that health workers, who were the first to get fully vaccinated, figure “regularly among those getting infected these days”. “Apart from that, vaccination has given a false sense of confidence among people of all sections, prompting many to abandon Covid protocols,’’ an official said.

Dr T S Aneesh, a member of the state’s expert committee on Covid, said that health workers, frontline workers, government officials and teachers on election duty, had been first to get fully vaccinated.

“The data on infection among the fully vaccinated is a reason to suspect whether the immunity level in the fully vaccinated is going down. Another factor is that health workers, who are among those with breakthrough infections, have better access to testing,’’ he said.

Aneesh said that in places or states where natural infection of Covid was very high, chances of breakthrough infections are very low.

“Kerala had immunity from vaccine rather than natural infection, and the state has been vulnerable to breakthrough cases. Breakthrough infection shows the effectiveness of the health system. In infections happening after vaccination, symptoms would be very mild. Such cases with mild symptoms can be detected only through effective testing strategies,’’ he said.

Dr N M Arun, a public health expert, said the latest trend highlights the importance of maintaining Covid-appropriate behaviour even after vaccination. “Vaccines reduce the intensity of the infection. The efficacy of the vaccine is related to minimising the severity of the infection rather than getting insulated from infection. It was due to vaccination that the number of positive cases to be admitted in hospitals came down,’’ he said.