COVID-19 vaccine clinical research
[6] Many vaccine candidates use adjuvants to enhance immunogenicity, as part of the delivery system or as an accompanying immune stimulant.
In July 2021, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) issued a joint statement reporting that a booster dose is not necessary for those who have been fully vaccinated.
The World Health Organization (WHO) defines heterologous prime-boost immunization as the "administration of two different vectors or delivery systems expressing the same or overlapping antigenic inserts.
[323][324] Some experts believe that heterologous prime-boost vaccination courses can boost immunity, and several studies have begun to examine this effect.
[333] A study in the UK is evaluating annual heterologous boosters by randomly combining the following vaccines: Oxford–AstraZeneca, Pfizer–BioNTech, Moderna, Novavax, VLA2001, CureVac, and Janssen.
Vaccine efficacy reflects disease prevention, a poor indicator of transmissibility of SARS‑CoV‑2 since asymptomatic people can be highly infectious.
[352] The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) set a cutoff of 50% as the efficacy required to approve a COVID-19 vaccine, with the lower limit of the 95% confidence interval being greater than 30%.
[356] The observed substantial efficacy of certain mRNA vaccines even after partial (1-dose) immunization[357][345] indicates a non-linear dose-efficacy relation already seen in the phase I-II study.
"[402] By late August 2021, the Delta variant accounted for 99 percent of U.S. cases and was found to double the risk of severe illness and hospitalization for those not yet vaccinated.
[403] In November 2021, a study by the ECDC estimated that 470,000 lives over the age of 60 had been saved since the start of the vaccination roll-out in the European region.
[405] On 10 December 2021, the UK Health Security Agency reported that early data indicated a 20- to 40-fold reduction in neutralizing activity for Omicron by sera from Pfizer 2-dose vaccinees relative to earlier strains.
[407] According to early December 2021 CDC data, "unvaccinated adults were about 97 times more likely to die from COVID-19 than fully vaccinated people who had received boosters".
[408] A meta-analysis looking into COVID-19 vaccine differences in immunosuppressed individuals found that people with a weakened immune system are less able to produce neutralizing antibodies.
[423][424] A UK study found COVID vaccination is safe for pregnant women and is associated with a 15% decrease in the odds of stillbirth.
Researchers at St George's, University of London, and the Royal College of Obstetricians and Gynaecologists investigated 23 published studies and trials involving 117,552 vaccinated pregnant women.
[425][426] A US study of 46,079 pregnancies concluded that COVID vaccination is safe and does not raise the risk of preterm birth or small size babies.
[454] As of February 2021[update], the US Food and Drug Administration believed that all FDA authorized vaccines remained effective in protecting against circulating strains of SARS-CoV-2.
Preliminary data from a clinical trial indicates that the Novavax vaccine is ~96% effective for symptoms against the original variant and ~86% against Alpha.
[469] On 7 February 2021, the Minister for Health for South Africa suspended the planned deployment of about a million doses of the vaccine whilst they examine the data and await advice on how to proceed.
[6][472] Limited evidence from various preliminary studies published in 2021 reviewed by the WHO have indicated likely retained efficacy/effectiveness against disease from Gamma with CoronaVac and Sinopharm BIBP, with no data for other vaccines yet.
Relevant to how vaccines can end the pandemic by preventing asymptomatic infection, they have also indicated retained antibody neutralization against Gamma with Oxford–AstraZeneca and CoronaVac (no to minimal reduction) and slightly reduced neutralization with Pfizer–BioNTech and Moderna (minimal to moderate reduction), with no data for other vaccines yet.
[481] COVID-19 vaccine effectiveness was studied in adults without immunocompromising conditions in 10 US states between 18 December 2021 – 10 June 2022, when Omicron was prevalent.
[482] One study found that the in vitro concentration (titer) of neutralizing antibodies elicited by a COVID-19 vaccine is a strong correlate of immune protection.
It is higher for Sputnik V and the convalescent response, and is within the predicted interval for the other vaccines evaluated (Pfizer–BioNTech, Moderna, Janssen, CoronaVac, Covaxin, Novavax).
[486][487][488] All vaccines, including COVID-19 ones, can have minor side effects related to the mild trauma associated with the introduction of a foreign substance into the body.
Reporting of all adverse events, careful followup and statistical analysis of occurrences are required to determine whether or not a specific health problem is more likely to occur after a vaccine is administered.
Before COVID-19 vaccines such as Moderna and Pfizer/BioNTech were authorized for use in the general population, they had to pass phase III studies involving tens of thousands of people.
Subsequent examinations of the use of COVID vaccines in pregnant people and in children have shown similar outcomes to the general population and do not suggest greater risk for these groups.
