Vaccines That Have Used Double-Blind Studies for Clinical Trials
Many major vaccines have utilized double-blind, placebo-controlled studies in their clinical trials, including influenza vaccines, COVID-19 vaccines, and meningococcal vaccines, which is considered the gold standard for evaluating vaccine efficacy and safety.
Influenza Vaccines
Both inactivated influenza vaccines and live attenuated influenza vaccines (LAIV) have been evaluated through randomized, double-blind, placebo-controlled trials 1.
A randomized, double-blind, placebo-controlled trial among 4,561 healthy working adults aged 18-64 years assessed multiple endpoints for LAIV, including reductions in illness, absenteeism, healthcare visits, and medication use 1.
Another randomized, double-blind, placebo-controlled challenge study among 92 healthy adults assessed the efficacy of both LAIV and inactivated influenza vaccine, showing 85% and 71% efficacy, respectively 1.
In children, a randomized, double-blind, placebo-controlled trial among 1,602 healthy children initially aged 15-71 months assessed the efficacy of trivalent LAIV against culture-confirmed influenza during two seasons, showing 92% efficacy over the two-season study 1.
Meningococcal Vaccines
Meningococcal conjugate vaccine (MCV4) was evaluated through randomized, double-blind, controlled trials 1.
The concomitant administration of MCV4 and tetanus and diphtheria toxoids was evaluated in a double-blind, controlled trial of participants aged 11-17 years 1.
Among adults aged 18-55 years, a randomized controlled trial assessed immunogenicity of MCV4 and typhoid vaccine in a double-blind design 1.
COVID-19 Vaccines
Multiple COVID-19 vaccines have been evaluated through randomized, double-blind, placebo-controlled trials 2, 3, 4, 5.
A phase III, randomized, double-blind, placebo-controlled clinical trial evaluated the efficacy and safety of an inactivated SARS-CoV-2 vaccine manufactured by Sinovac in healthcare professionals 3.
A multinational, randomized, placebo-controlled, double-blind, phase 3 trial among healthy adults evaluated the monovalent COVID-19 mRNA vaccine ABO1020, showing 66.18% efficacy against symptomatic COVID-19 4.
A randomized, placebo-controlled, double-blind, multicentre, phase 3 clinical trial of the BIV1-CovIran inactivated virus-particle vaccine showed 50.2% efficacy against symptomatic COVID-19 and 70.5% efficacy against severe disease 5.
A randomized, double-blind phase I clinical trial evaluated two COVID-19 vaccine candidates based on recombinant dimeric RBD (d-RBD) 6.
Hepatitis A Vaccines
The efficacy of HAVRIX (hepatitis A vaccine) was evaluated in a double-blind, controlled, randomized clinical trial conducted in Thailand among approximately 40,000 children aged 1-16 years 1.
A double-blind, placebo-controlled, randomized clinical trial using VAQTA (hepatitis A vaccine) was conducted among approximately 1,000 children aged 2-16 years, showing 100% protective efficacy against clinical hepatitis A 1.
Importance of Double-Blind Studies in Vaccine Development
Double-blind studies are crucial for minimizing bias in vaccine evaluation, as neither the participants nor the researchers know who receives the vaccine or placebo 1.
These studies provide the most reliable evidence on vaccine efficacy, safety, and immunogenicity by controlling for placebo effects and observer bias 1, 4.
Double-blind studies have been instrumental in establishing the efficacy of vaccines against clinical disease endpoints, hospitalization, and death 1, 5.
Common Methodologies in Vaccine Double-Blind Studies
Most vaccine double-blind studies use saline or aluminum hydroxide adjuvant as placebo controls 3, 5.
Efficacy endpoints typically include laboratory-confirmed disease, symptomatic disease, severe disease, hospitalization, or death 4, 5.
Safety assessments include monitoring of local and systemic adverse events, with specific attention to severe adverse events 1, 6.
Immunogenicity is often measured through antibody titers, neutralizing antibody levels, or other immunological markers 1, 6.