Health

Evidence shows COVID-19 booster protection may wane after 4 months

Centers for Disease Control and Prevention (aka CDC, the US national public health agency responsible for the protection of public health and safety through the control and prevention of disease, injury, and disability), published data that suggests some COVID-19 booster shots lose much of their potency after about four months.

The study titled ‘Waning 2-Dose and 3-Dose Effectiveness of mRNA Vaccines Against COVID-19’ was published on 18th February. 

This data offered the first real-world evidence of the mRNA shots’ waning efficacy against moderate to severe COVID-19 in the US. In the study, researchers measured how effective COVID-19 mRNA vaccines – either Pfizer or Moderna – were at preventing both hospitalization and visits to emergency departments or urgent care facilities.

According to a New York Times’ report, “the study focused on people who sought medical care for symptoms of COVID-19, so if that population was skewed toward older adults or those who have weak immune systems, the booster shots may have seemed less effective than they really are.

The team of CDC researchers analysed 241,204 visits to emergency departments or urgent care facilities and 93,408 hospitalizations among adults older than 18. The study did not include milder infections.

Protection against emergency department and urgent care visits declined from 69 percent within two months of the second dose to 37 percent after five months or more. Booster shots restored those levels to 87 percent.

The effectiveness of boosters also waned. Protection against emergency department and urgent care visits dropped to 66 percent within four or five months, and to just 31 percent after five or more months of receiving the third/booster shot, the researchers found. The latter estimate may not be reliable because few people received boosters more than five months ago, and so the data is limited, the researchers said.”

“There may be the need for yet again another boost — in this case, a fourth-dose boost for an individual receiving the mRNA — that could be based on age, as well as underlying conditions,” Dr. Anthony S. Fauci told reporters.


So far, more than 10 million Australians over the age of 16 have received a booster dose, and millions more are currently eligible. But with Chief Medical Officer Professor Paul Kelly predicting another Omicron wave during winter, the research has raised questions about what the future may hold for the booster roll-out in Australia.

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