Coronavirus: Are three doses of the Covid-19 vaccine better than two? Debate over third shot

  • The spread of the Delta variant raises the question of a third booster shot; some say priority should go to people who have yet to get a first
  • Countries like France and Israel are already planning third jabs for immunocompromised and elderly people
Agence France-Presse |

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A person receives a dose of the vaccine against Covid-19 at the University of Las Americas in Quito, Ecuador. The Ecuadorian government aims to vaccinate nine million people, equivalent to 60 per cent of the population, by the end of August. Photo: EPA

As the Delta variant spreads throughout the world, the prospect of a third “booster” shot is gaining interest even in places where a large proportion of people are vaccinated.

Experts say it is too soon to know for sure if countries will need to organise a third vaccine round later in the year. Some suggest that priority should be given to the hundreds of millions of people who have not even had access to their first jab yet.

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Why three?

Earlier this month, manufacturers Pfizer/BioNTech said they would ask US and European authorities for permission to provide a third dose of their vaccine, saying the move was aimed at ensuring stronger immunity.

The developers said two doses of their vaccine protected against severe Covid-19 for at least six months, but that faced with emerging variants, they anticipated some decline in the jab’s efficacy over time.

The White House’s chief medical advisor Anthony Fauci, speaking on news channel CNBC on Tuesday, said Pfizer/BioNTech’s third-dose application was “an appropriate preparation (for) the eventuality that you might need a booster”, but that it wasn’t accurate to say that everyone would definitely need a booster shot.

He added that there were still too many people who are not fully vaccinated with two doses, let alone three.

Unpacking Covid-19 vaccines at La Aurora International Airport in Guatemala City, Guatemala. The United States shipped three million jabs to the Central American country on Tuesday, as part of US President Joe Biden's strategy to become a provider of free vaccines. Photo: EPA

What do authorities say?

There is currently no sign that medical agencies will recommend a third dose for everyone who has already received two.

The European Medicines Agency and the European Centre for Disease Control said it is still too early to tell if a third dose is needed.

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“There is not enough data yet from vaccination campaigns and ongoing studies to understand how long protection from the vaccines will last, also considering the spread of variants,” they said in a joint statement.

Didier Houssin, director of the World Health Organisation’s emergency committee, said he didn’t believe there was enough evidence to justify recommending a third dose at this point.

He also warned that talk of a third dose could “aggravate concerns over access to vaccines” at a time when most countries have only a tiny percentage of people fully inoculated.

People queue to receive a dose of the Sputnik V coronavirus vaccine in Mexico City, Mexico. Photo: Reuters

Useful for vulnerable people and the elderly

Although mass third dose campaigns don’t appear to be on the horizon, several countries have already started giving third doses to certain people.

These include individuals who have a weakened immune system, including those who have undergone organ transplants, or suffer from cancer or renal problems.

France and Israel have already begun giving third doses to certain people.

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“Recent data showed that the immune response provoked by two doses is insufficient among severely immunosuppressed individuals,” France’s vaccine committee said in May.

For its part, Israel justified its decision by pointing to “a large number of cases in recent weeks” as well as the risk posed to immunocompromised patients.

France went a step further on Monday in announcing that a “booster campaign” would start from September for people fully vaccinated earlier in the year, and that it would begin the drive with over 80s.

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“Scientific data to support this proposal is still limited, but taking into account studies showing a fall in antibody levels in this population, and the potentially serious impact on the care system, it appears reasonable,” the council said.

It added that it is possible younger people would eventually have access to a third shot, depending on how the pandemic progresses.

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