In a recent study posted to the Research Square* preprint server, researchers reported the waning of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the six months following a booster dose of the messenger ribonucleic acid (mRNA) coronavirus disease 2019 (COVID-19) vaccine. They noted a three-fold decrease in the reactivity of vaccine-elicited antibodies against the Omicron BA.1 and BA.2 variants.
The COVID-19 mRNA vaccines BNT162b (Pfizer BioNTech) and mRNA-1273 (Moderna) have elicited effective immune responses against the targeted strains of SARS-CoV-2 after the two-dose primary vaccination. However, waning immunity of the primary doses and the emergence of new immune-evading Omicron subvariants have challenged the efficacy of the vaccine.
The United States (U.S.) Food and Drug Administration (FDA) has approved a booster dose to increase protection against infections from Omicron subvariants. Although studies have shown that a booster dose significantly increases the neutralizing antibodies, the neutralizing capacity of these antibodies against different SARS-CoV-2 variants is known to differ.
Therefore, an assessment of the durability of booster dose-induced neutralizing antibodies is essential for formulating public health policies on booster vaccinations.
About the study
In the present study, the researchers recruited 323 healthcare workers from Orange County, California, vaccinated with two primary doses of the BNT162b or mRNA-1273 vaccine. Serological testing of blood samples was conducted before administering the booster dose and at multiple time points up to six months following the booster vaccine. Information such as demographic data, testing frequency, characteristics related to work, symptom history, and exposure risk was gathered through surveys.
A coronavirus antigen microarray was used to measure the immunoglobulin (Ig) G and IgM antibodies against a panel of 37 antigens, including those from SARS-CoV-2 and other coronaviruses and respiratory viruses.
The antigen panel comprised 10 SARS-CoV-2 antigens, including different fragments of the spike protein and the nucleocapsid protein, as well as four severe acute respiratory syndrome (SARS), three Middle East respiratory syndrome (MERS), 12 common coronaviruses, and eight influenzas virus antigens.
A surrogate virus neutralization test was used to determine the neutralization capacity of the anti-SARS-CoV-2 antibodies. The serum samples from a subset of the participants were also measured for antibodies against the spike protein receptor binding domain of the ancestral Wuhan-Hu-1 strain, the Delta variant, and the Omicron BA.1 and BA.2 subvariants. Additionally, a pseudoneutralization assay was used to determine the correlation between neutralizing and binding antibodies.
Results
The results reported an increase in the IgG antibody levels in the two weeks following the administration of the booster dose and continuing up to two months. However, between the second and the fourth month, the antibody levels were seen to decrease significantly. The waning of the antibodies continued till the sixth month from the booster dose, but the antibody titers at the end of six months remained higher than the pre-booster dose levels.
Healthcare workers with a history of SARS-CoV-2 infections had higher antibody titers at four and six months after the booster dose than those who did not have previous SARS-CoV-2 infections. Additionally, participants with severe vaccination side effects also had significantly higher levels of antibodies at two- and four-months post-booster than those with no side effects.
The advanced microarray analysis on the serum samples from a subset of the participants revealed that before the booster dose, the antibody titers against the Wuhan-Hu-1 strain were similar to those against the Delta variant. Still, the antibody levels against the Omicron subvariants were significantly lower.
In the two weeks following the booster dose, the antibodies against the Delta variant and the Omicron subvariants underwent a 1.3-fold and six-fold reduction, respectively, compared to the antibodies against the ancestral strain. This trend was observed till the six-month time point.
Similar to the trend seen in antibody levels, the neutralization capacity also increased up to two months following the administration of the booster dose and then decreased till the sixth month. The pseudoneutralization assay reported a correlation between binding and neutralizing antibodies.
Conclusions
Overall, the results indicated that the antibody levels and neutralization capacity increased significantly up to two months after the booster dose of the mRNA vaccine and then waned. Furthermore, the booster dose significantly increased the antibodies against the ancestral strain, but the antibodies against the Delta variant and Omicron subvariants decreased by 1.3- and six-fold, respectively.
Individuals with hybrid immunity from vaccinations and previous SARS-CoV-2 infections had more robust antibody responses than those without a history of SARS-CoV-2 infections. The development of variant-specific vaccines is necessary to prevent breakthrough infections.
*Important notice
Research Square publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
Some Ontario doctors have started offering a free shot that can protect babies from respiratory syncytial virus while Quebec will begin its immunization program next month.
The new shot called Nirsevimab gives babies antibodies that provide passive immunity to RSV, a major cause of serious lower respiratory tract infections for infants and seniors, which can cause bronchiolitis or pneumonia.
Ontario’s ministry of health says the shot is already available at some doctor’s offices in Ontario with the province’s remaining supply set to arrive by the end of the month.
Quebec will begin administering the shots on Nov. 4 to babies born in hospitals and delivery centers.
Parents in Quebec with babies under six months or those who are older but more vulnerable to infection can also book immunization appointments online.
The injection will be available in Nunavut and Yukon this fall and winter, though administration start dates have not yet been announced.
This report by The Canadian Press was first published Oct. 21, 2024.
-With files from Nicole Ireland
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
ISLAMABAD (AP) — Polio cases are rising ahead of a new vaccination campaign in Pakistan, where violence targeting health workers and the police protecting them has hampered years of efforts toward making the country polio-free.
Since January, health officials have confirmed 39 new polio cases in Pakistan, compared to only six last year, said Anwarul Haq of the National Emergency Operation Center for Polio Eradication.
The new nationwide drive starts Oct. 28 with the aim to vaccinate at least 32 million children. “The whole purpose of these campaigns is to achieve the target of making Pakistan a polio-free state,” he said.
Pakistan regularly launches campaigns against polio despite attacks on the workers and police assigned to the inoculation drives. Militants falsely claim the vaccination campaigns are a Western conspiracy to sterilize children.
Most of the new polio cases were reported in the southwestern Balochistan and southern Sindh province, following by Khyber Pakhtunkhwa province and eastern Punjab province.
The locations are worrying authorities since previous cases were from the restive northwest bordering Afghanistan, where the Taliban government in September suddenly stopped a door-to-door vaccination campaign.
Afghanistan and Pakistan are the two countries in which the spread of the potentially fatal, paralyzing disease has never been stopped. Authorities in Pakistan have said that the Taliban’s decision will have major repercussions beyond the Afghan border, as people from both sides frequently travel to each other’s country.
The World Health Organization has confirmed 18 polio cases in Afghanistan this year, all but two in the south of the country. That’s up from six cases in 2023. Afghanistan used a house-to-house vaccination strategy this June for the first time in five years, a tactic that helped to reach the majority of children targeted, according to WHO.
Health officials in Pakistan say they want the both sides to conduct anti-polio drives simultaneously.
WASHINGTON (AP) — Millions of people with private health insurance would be able to pick up over-the-counter methods like condoms, the “morning after” pill and birth control pills for free under a new rule the White House proposed on Monday.
Right now, health insurers must cover the cost of prescribed contraception, including prescription birth control or even condoms that doctors have issued a prescription for. But the new rule would expand that coverage, allowing millions of people on private health insurance to pick up free condoms, birth control pills, or “morning after” pills from local storefronts without a prescription.
The proposal comes days before Election Day, as Vice President Kamala Harris affixes her presidential campaign to a promise of expanding women’s health care access in the wake of the U.S. Supreme Court’s decision to undo nationwide abortion rights two years ago. Harris has sought to craft a distinct contrast from her Republican challenger, Donald Trump, who appointed some of the judges who issued that ruling.
“The proposed rule we announce today would expand access to birth control at no additional cost for millions of consumers,” Health and Human Services Secretary Xavier Becerra said in a statement. “Bottom line: women should have control over their personal health care decisions. And issuers and providers have an obligation to comply with the law.”
The emergency contraceptives that people on private insurance would be able to access without costs include levonorgestrel, a pill that needs to be taken immediately after sex to prevent pregnancy and is more commonly known by the brand name “Plan B.”
Without a doctor’s prescription, women may pay as much as $50 for a pack of the pills. And women who delay buying the medication in order to get a doctor’s prescription could jeopardize the pill’s effectiveness, since it is most likely to prevent a pregnancy within 72 hours after sex.
If implemented, the new rule would also require insurers to fully bear the cost of the once-a-day Opill, a new over-the-counter birth control pill that the U.S. Food and Drug Administration approved last year. A one-month supply of the pills costs $20.
Federal mandates for private health insurance to cover contraceptive care were first introduced with the Affordable Care Act, which required plans to pick up the cost of FDA-approved birth control that had been prescribed by a doctor as a preventative service.
The proposed rule would not impact those on Medicaid, the insurance program for the poorest Americans. States are largely left to design their own rules around Medicaid coverage for contraception, and few cover over-the-counter methods like Plan B or condoms.
