How long is the covid-19 vaccine effective for?
The national vaccination effort has been a success so far, but as the US approaches herd immunity there is still little known about the long-term effectiveness of the shots.
On Tuesday the Centers for Disease Control and Prevention (CDC) published new data which showed that 38% of the US population is fully vaccinated. In addition to that, at least 60% of American adults have received at least one shot of a coronavirus vaccine.
President Biden set the target of getting at least one dose of a vaccine to 70% of adults by 4 July, and with six weeks to go he appears on track on hit that target. Accordingly, the seven-day average of daily new cases is continuing to fall and is now down to around 28,000 new cases a day, compared to 295,000 during the January peak.
The vaccine effort is clearly having a positive impact, but scientists are still uncertain about how long the vaccination is effective for.
How long does vaccine immunity last for?
Clinical trials and re-world studies have shown that both the Pfizer/BioNTech and the Mordena vaccines are incredibly effective at preventing infection from covid-19, but less is known about the long-term implications.
In April the CDC published a new study on around 4,000 vaccinated healthcare professional, continuing to test them once a week for 13 weeks. These trials found that they are around 80% effective after just a single dose, and 90% effective after the recipient has had both doses.
Pfizer/BioNTech have carried out their own study which found that those high levels of immunisation continue for at least six months, proving to be 95.3% effective against the Food and Drug Administration’s definition of ‘severe covid-19’.
Dr Susan Bailey, President of the American Medical Association, said of the news: “The good news is that in the 6-month status report from Pfizer, immunity stays very strong, and we anticipate that it will continue to stay strong.”
She added: “But it’s definitely longer than that — it’s not just going to drop off after 6 months. I would have been concerned if efficacy had dropped by a third or half.”
CDC are “still learning” about covid-19 immunisation
The guidelines for vaccine use and the format of the vaccine rollout have largely been dictated by the CDC’s findings, and they are constantly re-evaluating their advice to reflect the latest findings. Just last week they altered the guidance to say that fully vaccinated Americans may not need to be required to wear a mask in some situations.
However they still advise that people wear masks in public wherever possible until they have gathered more information about the immunisation and infection rates of covid-19 vaccines.
The CDC report says: “Scientists are still learning how well vaccines prevent you from spreading the virus that causes COVID-19 to others, even if you do not have symptoms.”
“For these reasons, people who have been fully vaccinated against COVID-19 should keep taking precautions until we know more, like wearing a mask in indoor public places, avoiding large indoor gatherings, and washing your hands often.”