Protection from Pfizer, AstraZeneca jabs declines after six months: UK researchers

A UK study says that the protection from Pfizer and AstraZeneca jabs against COVID-19 begins to decline within six months after complete immunisation. ZOE COVID, a UK-based research organisation, produced the study after thoroughly analysing 1.2 million samples. Underlining the need for booster doses, ZOE COVID has presented data that proved the effectiveness of the Pfizer vaccine was 88% after the second dose, and for AstraZeneca, it was 77%. However, the protection decreased to 74% and 67% for Pfizer and AstraZeneca, respectively, after five to six months.

The study also produced some more alarming results. It suggested that the protection level in older people could also drop below 50%. Furthermore, the steep drop could be observed among healthcare workers by the winter, said Tim Spector, principal investigator for the ZOE COVID study. 

Antibody levels decline within 2-3 months

According to a similar study conducted by researchers at the University College London (UCL), total antibody concentrations declined in the sixth week after complete immunisation with Pfizer and AstraZeneca vaccines. The researchers from the UCL studied that antibody levels dropped at a "predictable exponential rate" and could begin to "wear off the protective effects" of the vaccines against the new variants.

For Pfizer, antibody levels reduced from a median of 7,506 Units per millilitre (U/mL) at 21–41 days to 3,320 U/mL at 70 or more days. For the AstraZeneca vaccine, antibody levels reduced from a median of 1,201 U/mL at 0–20 days to 190 U/mL at 70 or more days, over a five-fold reduction.

US to roll out booster dose from September 20

Following a similar assessment by the US Health Department, the officials have decided to introduce booster shots for additional vaccine-induced protection for "prolonged durability". "Based on the latest assessment, current protection against severe disease, hospitalization, and death could diminish in the months ahead. Especially among those who are at high risk or were vaccinated during early phases of the vaccine rollout," an official statement said.

About the eligibility, the government notice added that all individuals who were fully vaccinated in the earliest phase of vaccine rollout, including Covid warriors and frontline workers, will be deemed fit for the booster shot. Although, the decision for the people who have received Johnson and Johnson shots is still awaited.

Meanwhile, Britain has started to plan for a booster campaign in September. As per reports, the vaccines will be deemed mandatory for elderly and vulnerable individuals.

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