Thousands of people in California may have received an incorrect dose of the COVID vaccine due to miscommunication in a health care centre, the vaccine provider announced in a statement. The incomplete dosage was only linked to the Pfizer vaccine.

Kaiser Permanente Walnut Creek Medical Center said that about 3,900 individuals — who received their jab between October 25 and December 10 last year– “may have received a slightly less than recommended dose of vaccine”, according to local media reports.

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The vaccine centre said that the individuals may have received less than the quantity recommended by United States healthcare experts.

The Centers for Disease Control and Prevention says that a 0.30 ML dose should be given at a time, while those who got incomplete vaccines may have received 0.01 to 0.04 ML less, Kaiser Permanente said in a statement.

The incomplete dosage was given by “some staff misunderstanding instructions”, the company said. To make sure the situation does not repeat, the centre says that the staff has been retrained and monitoring has been increased.

United States Centers for Disease Control and Prevention and other healthcare experts were consulted after officials were made aware of the situation. 

The statement from the vaccine centre reads, “All experts agreed the difference between the recommended dose and the dose an individual may have received was not significant and not likely to reduce their protection against COVID-19”, according to local media reports.

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The centre further promised to provide a repeat dose and flexible appointments to those who received the incomplete dose.

Such incidents have been previously reported across the United States before, once in Virginia and another one in California. Virginia’s Health Department said in a statement that kids received a smaller dosage over a two day period.