Efficacy of a Fourth Dose of Covid-19 mRNA Vaccine against Omicron

Safety, immunogenicity, and reactogenicity of BNT162b2 and mRNA-1273 COVID-19 vaccines given as fourth-dose boosters following two doses of ChAdOx1 nCoV-19 or BNT162b2 and a third dose of BNT162b2 (COV-BOOST): a multicentre, blinded, phase 2, randomised trial

“…The peak anti-spike protein IgG concentration after a fourth vaccine dose was also higher than after a third dose for full-dose BNT162b2 and half-dose mRNA-1273 among participants in an Israeli observational study who had previously received three doses of BNT162b2 and had low anti-spike IgG titres before the fourth dose. 6 The fold changes before and after the fourth dose in the Israeli study were lower to those found in our study, probably due to the shorter interval between third and fourth doses in the Israeli study as a longer duration between vaccine doses is recognised to increase immunogenicity. 10 , 11 A large increase from baseline in neutralising antibody titres after a fourth dose of mRNA COVID-19 vaccine was also observed in a German observational study, although neutralising capacity against omicron subvariants remained low.…”

“…Observational data from Israel have shown a boosting effect on immunogenicity 6 and moderate protection against symptomatic infection from a fourth dose of mRNA COVID-19 vaccines administered approximately 4 months after a third dose. 7 , 8 The clinical need, timing, and dose of the fourth COVID-19 vaccine remain uncertain, 9 as does the gain in vaccine effectiveness compared with a third dose.…”

Covid-19: Pfizer asks US regulator to authorise fourth vaccine dose for over 65s

“…On 16 March a research letter published in the New England Journal of Medicine reported the effects of using either Pfizer or Moderna vaccines as a fourth vaccine dose in 174 healthcare workers in Israel, given four months after a booster dose. Each participant was matched to two controls 4…”

Implications of COVID-19 vaccine effectiveness waning for public health

“…Yet, most studies show that protection against severe disease, hospitalisation, and death is maintained at high levels, even with high infection rates, 3 and waning effectiveness against infection is in line with what has been observed for other vaccines, such as those against influenza, due to declining immunity. 4 , 5 , 6 Therefore, assessing the duration of vaccine protection and determining the ideal timing for boosters or annual vaccination against SARS-CoV-2 is crucial for public health researchers and officials.…”

“…This network could track worldwide, year-round SARS-CoV-2 and suggest the best-matched vaccine composition against changing dominant variants, or it could promote different strategies, 2 such as the development of a pan-coronavirus vaccine for enduring, robust protection against multiple strains. Since repeated same-composition booster administration seems not to be advisable, 5 efforts should be devoted to comparatively evaluate different immunisation programmes (ie, COVID-19 annual vaccination campaign) to inform decision makers’ planning and public health practice in offering the best possible collective health.…”