Pfizer vaccine is far more effective after one dose than first thought - new findings show

By Claire Schofield
Friday, 19th February 2021, 4:12 pm
Updated Friday, 19th February 2021, 4:12 pm
The Pfizer/BioNTech vaccne is 85 per cent effective in preventing people from developing Covid-19 symptoms (Photo: Getty Images)
The Pfizer/BioNTech vaccne is 85 per cent effective in preventing people from developing Covid-19 symptoms (Photo: Getty Images)

The Covid-19 vaccine developed by Pfizer/BioNTech is 85 per cent effective in preventing people from developing symptoms of the virus after the first dose, a study has found.

The findings, published in the journal Lancet, appear to support the UK’s decision to delay the second dose of the vaccine, as a high level of protection is gained from just one shot.

Reducing infections

The study, which assessed more than 7,000 healthcare workers at the Sheba Medical Centre in Israel, also found that just one dose of the vaccine reduced all infections, including those without symptoms, by 75 per cent.

Findings indicate that delaying the second vaccine dose up to 12 weeks to increase the number of people getting the jab was the right move, as the first dose provides a high level of immunity.

Deborah Dunn-Walters, chairwoman of the British Society for Immunology Covid-19 and Immunology Taskforce, explained: “Due to the high percentage of the Israeli population vaccinated so far, we have been awaiting data from there to indicate the first signs of how effective Covid-19 vaccines are outside of a clinical trial setting and how dosing schedule plays into this.

“It should be noted that this study was carried out on people of working age, so it will be informative to see a similar study in older people after one dose.

“Although further research is needed, overall these new findings should provide reassurance around the UK’s decision to offer the two doses of the vaccine 12 weeks apart.”

Dr Peter English, consultant in communicable disease control and former editor of Vaccines in Practice Magazine, described the findings as “good news” but added that available data is “quite limited”.

He said: “This is good news. It supports earlier data suggesting that, from six weeks or so after vaccination, vaccine efficacy is likely to be at least 85 per cent – possibly considerably better – at least in vaccine recipients of working age.

“This is a letter, rather than a research paper – as such the data are quite limited, and I would expect far more details to be published in due course.”

Dr English added: “As far as I can tell, this particular letter does not include data on severe and mild infection – from other evidence (and experience with vaccination more generally) we would expect the vaccination to be more protective against severe disease than against mild disease, and more protective against mild disease than against asymptomatic infection.

“We may see more information on this when a more complete publication is made available.”

Two doses still needed

While a good level of protection against Covid-19 is gained from just one dose, scientists have stressed that it is highly important people do return to get their second shot.

Ms Dunn-Walters said: “While the results of this study show that a good level of immunity is present after one dose of the Pfizer/BioNTech vaccine, it is still the case that the highest and longest lasting protection from getting ill with Covid-19 will only be provided by getting two doses of the vaccine.

“It is critical that all people eligible for Covid vaccination do return to get their second dose when asked to do so by their medical providers.”

Almost 16.5 million people across the UK have now been given their first dose of a Covid-19 vaccine, which includes all four top priority groups.

The government is now aiming to offer the vaccine to the next five priority groups by the end of April, including the over 50s and people deemed clinically vulnerable.