The Pfizer-BioNTech mRNA vaccine has become the first in the US to receive emergency nod for a booster rollout, although for only selected groups of people. Several countries, including Israel, UK, France, Germany have introduced booster shots but not all are extending it to their entire eligible population. While studies suggest that immunity offered by the normal course of vaccination wanes over time, experts have called for more data to decide whether an additional dose is necessary. On the other hand, the WHO has said that countries should desist from rolling out booster doses while poorer countries are still struggling to offer vulnerable populations their first shot.
Who Is Eligible For The Booster Shot?
Approval for the booster dose of the Pfizer-BioNTech shot was sought for people aged 16 years and above, but the US authorities have extended clearance now for only people aged 65 years and above and those deemed to be at high risk of contracting Covid-19.
The high-risk groups include individuals in the 18-64 years age bracket who are either seen as being more susceptible to catching the infection or workers and individuals “whose frequent institutional or occupational exposure to Sars-CoV-2 puts them at high risk of serious complications of Covid-19 including severe Covid-19" like healthcare workers, teachers, etc.
But Pfizer said in a press statement that US authorities will, “as a next step", be taking up “a potential recommendation for the use and rollout of boosters" for all Americans.
When Is The Booster Shot To Be Given?
The watchdog US Food and Drug Administration (FDA) has said that the third shot should be given at least six months after an individual has received the second jab of the primary two-dose regimen. The US had said that it would start administering booster doses in September after its vaccination campaign launched in December last year.
While US authorities were assessing Pfizer-BioNTech’s application for the supplemental biologics licence application (sBLA) for a third dose for people aged 16 years and above, they had in August allowed a booster to be given to “certain immunocompromised individuals like those who have undergone solid organ transplantation or those diagnosed with other diseases that may have weakened their immune systems".
It has been clarified by the company that this, earlier, approval was was for individuals at least 12 years of age and involved the delivery of the third dose “at least 28 days following the second dose". Thus, the earlier third shot nod is “separate and distinct" from the latest recommendation on boosters, Pfizer said, adding that “the third dose for immunocompromised individuals is meant to address the fact that these individuals sometimes do not build enough protection after two doses of the vaccine".
Why Is A Booster Dose Being Rolled Out?
As opposed to immunocompromised individuals, Pfizer said that the booster shot that has now been approved is for “those who have built enough protection after the primary vaccination series, but may have decreased protection over time due to waning of immunity".
While the jury is still out on how long protection lasts from normal vaccination and whether the jabs being provided currently offer protection against the newer variants, Pfizer said it had found in trials that the booster dose “induced significant Sars-CoV-2 neutralising antibody titres against the initial Sars-CoV-2 virus (wild type), as well as the Beta and Delta variants". It said that the antibody levels against the initial virus type one month after the booster dose were “3.3 times the levels seen one month after the second dose".
Is It Different? And What About Safety?
The third shot of the Pfizer vaccine will have “the same formulation and dosage strength as the doses in the primary series", Pfizer said, adding that the adverse reactions seen within seven days of receiving it were “typically mild to moderate, and the frequency of reactions was similar to or lower than after dose two".
Why Is There A Debate Around Booster Doses?
The makers of the two other vaccines being used in the US — Moderna and Johnson and Johnson — have also sought an emergency nod for a booster for their two-dose mRNA and single-dose inactivated viral vector vaccine, respectively. But opinion is sharply divided on the case for an additional shot.
Reports say that available data only support boosters for older people and those with compromised immune systems, although Israel is handing out a third shot of the Pfixer vaccine to all aged 12 years and above who have received the primary two-dose series.
Israeli authorities have said that there was a decline in overall infections as well as severe illness in more than 1.1 million people aged 60 and above who had received a booster dose. Some health officials argue that extra shots are also important because they can help reduce spread of the disease by countering the rise of breakthrough infections, even if they are mild or asymptomatic.
The World Health Organisation (WHO) has strongly criticised the move to introduce booster shots, saying that the need of the hour for ending the pandemic is to vaccinate as many people worldwide as quickly as possible. Giving an additional shot in the absence of real world data on their efficacy served to deprive vulnerable groups in the poorer countries who could have benefited from those shots, it argues.