The efficacy of a new vaccine is defined by its effectiveness. In the case of COVID-19, a vaccine efficacy of 67% may be sufficient to slow the pandemic, but this assumes that the vaccine confers sterilizing immunity, necessary to prevent transmission.
The effectiveness of vaccines
Authorized and approved vaccines have shown efficacy ranging from 62% to 90% for the cheaper Oxford-AstraZeneca vaccine (with various dosage regimens) and 95% efficacy for the more expensive Pfizer-BioNTech vaccine. The effectiveness of the Moderna vaccine is 95.6% for people aged between 18 and 64 years.
In mid-December 2020, a new variant of SARS-CoV-2 was identified in the UK. Preliminary data indicated that this variant showed an estimated increase in reproduction number (R) of 0.4 or greater and greater transmissibility of up to 70%, but there is still no evidence of a lower efficacy of the vaccine on it.
The safety of vaccines
In the United States between December 14, 2020 and January 18, 2021, 9943247 doses of the Pfizer-BioNTech vaccine and 7581429 doses of the Moderna vaccine were administered. During this period of time just 66 reactions attributable to anaphylaxis were reported: the affected subjects were promptly assisted and no deaths occurred.
Misinformation and hesitation about vaccines
Social media posts have promoted a conspiracy theory that a COVID-19 vaccine would already be available when it wasn’t. In addition, about 10% of the public perceives vaccines as unsafe or unnecessary and refuses vaccination, which increases the risk of further viral spread.
In mid-2020, some estimates from two surveys indicated that between 67% and 80% of people in the United States would accept a new vaccination against COVID-19, with a wide disparity in education level, employment status and place of residence.
A survey conducted by National Geographic and Morning Consult demonstrated a gender gap in readiness to receive a COVID-19 vaccine in the United States with 69% of men surveyed saying they would get vaccinated, compared to just the 51% of women.